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TOOLS  FOR 


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AND  WOODWORKERS 


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TOOLS 

FOR 

MACHINISTS  AND  WOODWORKERS 

INCLUDING 

MODERN  INSTRUMENTS  OF  MEASUREMENT. 


A  PRACTICAL  TREATISE  COMPRISING  A  GENERAL  DE¬ 
SCRIPTION  AND  CLASSIFICATION  OF  CUTTING  TOOLS 
AND  TOOL  ANGLES,  ALLIED  CUTTING  TOOLS  FOR 
MACHINISTS  AND  WOODWORKERS  ;  SHEARING  TOOLS  ; 
SCRAPING  TOOLS  ;  SAWS  ;  MILLING  CUTTERS  ;  DRILLING 
AND  BORING  TOOLS  ;  TAPS  AND  DIES  ;  PUNCHES  AND 
HAMMERS  ;  AND  THE  HARDENING,  TEMPERING  AND 
GRINDING  OF  THESE  TOOLS.  TOOLS  FOR  MEASURING 
AND  TESTING  WORK,  INCLUDING  STANDARDS  OF  MEA¬ 
SUREMENT;  SURFACE  PLATES  ;  LEVELS ;  SURFACE  GAUGES ; 
DIVIDERS;  CALIPERS;  VERNIERS;  MICROMETERS;  SNAP, 
CYLINDRICAL,  AND  LIMIT  GAUGES  ;  SCREW  THREAD, 
WIRE  AND  REFERENCE  GAUGES  ;  INDICATORS,  TEMPLETS, 
ETC.,  ETC. 

BY 

JOSEPH  G.  HORNER,  A.M.I.Mech.E. 

Author  of  “  Pattern  Making,"  Hoisting  Machinery,"  etc.,  etc. 
ILLUSTRATED  BY  FOUR  HUNDRED  AND  FIFTY-SIX  ILLUSTRATIONS. 


NEW  YORK 

THE  NORMAN  W.  HENLEY  PUBLISHING  CO. 
132,  NASSAU  STREET 
1906 


PREFACE. 


Teie  object  of  this  book  is  to  give  an  account  of  such 
Tools  as  are  commonly  used  by  Engineers  and  Wood¬ 
workers,  written  chiefly  from  the  standpoint  of  the  men 
who  have  to  use  them,  and  who  desire  to  understand  the 
principles  which  underlie  the  forms  in  which  those  Tools 
are  found.  Practical  instructions  for  their  employment,  as 
suggested  by  the  writer’s  own  experience,  have  been  added. 
The  work  (it  is  believed)  is  more  comprehensive  in  its  scope 
than  any  which  has  preceded  it,  the  subject  of  Instruments 
of  Measurement  being  treated  in  a  very  full  manner  and 
freely  illustrated  (as  are  all  sections  of  the  work)  with 
drawings  of  leading  types. 

Although,  in  strictness.  Tools  and  Measuring  In¬ 
struments  form  distinct  groups,  they  cannot  be  separately 
regarded  in  shop  practice,  since  modern  methods  of 
measurement  are  directly  related  to  certain  systems  of 
manufacture,  both  general  and  special  in  character.  The 
subjects  treated  here  have  never  previously  assumed  such 
great  importance  as  in  recent  years.  Tool-making  has 
been  developed  into  highly  specialised  branches  of  manu¬ 
facture,  different  firms  taking  up  different  classes  or  groups 
of  Tools  and  Instruments,  with  the  perfection  of  results 
and  fine  precision  that  come  of  specialisation.  Some  of 


VI 


PREFACE. 


these  results  will  be  found  here  illustrated  in  book-form 
for  the  first  time. 

The  great  and  growing  importance  of  Cutting  Tools  in 
modern  practice  is  evidenced  by  the  numerous  experiments 
to  which  they  have  been  subjected.  But  the  experience  of 
the  shops  still  remains  of  highest  value,  and  only  in  very 
general  terms  can  these  experiments  be  applied  as  yet  to 
practical  issues.  As  they  relate  to  Lathe  Tools  chiefly, 
some  account  of  them  will  be  found  in  another  work  (now 
in  the  press)  by  the  same  Author,  dealing  with  “  Engineers’ 
Turning.”  • 

It  should  be  mentioned  that  a  large  part  of  the  matter 
included  in  this  volume  consists  of  selections  from  various 
articles  contributed  by  the  Author  to  the  English  Mechanic 
and  the  Mechanical  World,  which  have  been  carefully  re¬ 
vised  and  supplemented  where  necessary,  but  several 
chapters  are  chiefly  or  entirely  new,  and  a  substantial 
proportion  of  the  illustrations  given  have  been  specially 
drawn  and  engraved  for  the  work. 

JOSEPH  HORNER. 


Bath,  November  1904. 


CONTENTS. 


Introduction. — A  General  Survey  of  Tools.  page 

The  Term  Tool  Defined— Distinction  between  a  Tool  and  a  Machine 
— and  an  Appliance— Instruments  for  Measurement  and  Test — 

Broad  Grouping — Machine-operated  Tools,  and  Modern  Manu¬ 
facture —  Percussive  Tools  —  Moulding  Tools  —  Interchangeable 
System — The  New  Steels  ------  i 

Chapter  I. — Tool  Angles. 

Knives  and  Razors — The  Chisel  Group — Planes — Chisels  for  Metal — 
Principles  Underlying  Tool  Angles — Tool  Formation — A  Com¬ 
promise — Lessons  from  the  Chisel — Angles  Controlled  by  Charac¬ 
teristics  of  Materials — Shavings  and  Chips — Action  of  the  Plane 
Compared  with  Metal  Cutting  Tools  —  Lessons  Learned  from 
Hand  Tools — Rigidity  of  Tools — Summary  of  Practical  Results — 

No  Hard  and  Fast  Rules — The  Importance  of  Support  Afforded 
to  the  Work  and  the  Tools — and  of  Lubrication — Tools  that  Em¬ 
body  the  Chisel  Action — The  Scrape — Abrasion — Shearing — De- 
trusion — Tools  which  Occupy  an  Uncertain  Position  -  -  6 


SECTION  L—THE  CHISEL  GROUP. 

Chapter  H. — Chisels  and  Allied  Forms  for  Woodworkers. 

Antiquity  of  Chisels — Primitive  Forms  of  Stone,  Bronze,  and  Iron — 
Single  and  Double-bevelled  Chisels — Cutting  Action — Angle  and 
Edge — The  Wedge  Principle — Splitting  Action — Operation  by 
Thrust  or  Pressure — and  Percussion — Importance  of  Rigidity — 
Angles  of  Grinding  and  Sharpening — Skill  required  for  Operation 
— Methods  of  Holding — and  of  Thrusting — Grain — Plane  Surfaces 
— Paring  and  other  Chisels  compared — The  Axes  and  Adzes — 
Control  of — Draw-knife — Carvers’  Chisels — Lock  Chisels — Turning 
Chisels — Sharpening  Chisels — Permanence  of  Edges — The  Gouges 
— Antiquity  of — Outside  and  Inside  Types — Firmer  and  Paring — 
Millwrights’  and  Coachmakers’ — Curves  of  Gouges — Value  of 
Paring  Gouge — Carvers’  Gouges — Their  Varieties — Method  of 
Operation — Turning  Gouges — How  to  Use 


20 


Vlll 


CONTENTS. 


Chapter  III. — Planes,  page 

Great  Variety  in — Setting  of  Chisel  or  Iron  in  its  Stock — Fastening  of 
the  Iron— Convexity  of  Same— Choking — Utility  of  Top  Iron — 

The  Question  of  Angles,  as  affected  by  Re-sharpening — Linear 
Guidance — Related  to  Length  of  Stock — Preservation  of  Truth  of 
Face — Planes  for  Concave  Sweeps — The  Profiles  of  Planes — Draw¬ 
backs  to  the  Moulding  Planes — Iron  Planes— Gripping  of  Planes — 
Pressure  on — Guidance  of — Aids  derived  from  Shooting,  and 
Angle  Boards — The  Aid  of  Strips — Checking  the  Truth  of  Planed 
Surfaces — Details  of  Planing — Faces— Ends — Setting  Irons  in 
Stocks — Removal  of  Irons — Good  and  Bad  Timber — Sharpening 
Moulding  Planes — Wear  and  Tear  of  Planes- — Shooting — Mouth¬ 
pieces — Selection — and  Preservation  of  Planes — Toothing  Planes  -  38 

Chapter  IV. — Hand  Chisels  and  Allied  Forms  for  Metal 

Working. 

The  Cold  Chisel — Cutting  Angles — Shape — Breadth — Method  of  Use 
— The  Cross-cut  Chisel — Diamond  Point — Cold  and  Hot  Setts — 
and  Gouges — Setts  for  the  Steam  Hammer — Nicking  Chisel — 

Drifts  or  Broaches  -------  54 

Chapter  V. — Chisel-like  Tools  for  Cutting  Metal  by 
Turning,  Planing,  &c. 

Roughing  and  Finishing  Type — Roughing  Tools — Finishing  Tools — 
Parting  Tools — Inside  Tools — Tools  for  Planer  and  Shaper — 
Cranking — Overhang — Stiffness  of  Tool  and  Support — Roughing 
and  Finishing  Tools — Straightforward  Tools — Cranked  Tools — 

Broad  Finishing — Slotting  Tools  -----  58 

Chapter  VI. — The  Shearing  Action,  and  Shearing  Tools. 

Shearing  a  Detailed  Operation — Diagonal  Cutting  with  Chisel — Fox 
Trimmer — Square  and  Skew-mouthed  Rebate  Plane — Turning 
Chisel — Reamers  and  Milling  Cutters — Roughing  Tools — Walker 
Planer  Tool — Profiled  Tool — Shear  Blades — Necessity  for  Support 
to  the  Substance  being  Shorn — Staggered  Cutting  in  Mills — Flat 
Drill — Combination  of  Shearing  with  Staggering  -  -  -  69 


SECTION  IL— SCRAPING  TOOLS. 

Chapter  VII. — Examples  of  Scraping  Tools. 


The  Nature  of  the  Operation — The  Metal-worker’s  Scrape — Some 
Wood-turner’s  Finishing  Tools — Arboring  Tools — Fly  Cutters 


75 


CONTENTS. 


IX 


SECTION  III.— TOOLS  RELATED  TO  BOTH 
CHISELS  AND  SCRAPES. 

Chapter  VIII. — Saws.  page 

Wide  Scope  of  the  Subject — Saw  Teeth,  Scrapes  and  Chisels — Shapes 
Varied  to  Suit  Materials — Examples — Spacing — Types  of  Saws — 
Reciprocating — Continuous — Variations  in  Speeds — Tension  of 
Blades — Thickness  of  Blades — Stiffening  of  Blades — Back  Saws — 

Wear  of  Teeth — Degree  of  Set — Keeping  Saws  in  Order — Set — 

Its  Amount  and  Regularity— Methods  of  Setting — by  Bending — 
by  Hammering — Test  of — Sharpening  Saws — Topping  the  Teeth 
— by  Stoning — by  Filing — Files  for  Sharpening— Angles  for  Filing 
— Gulleting — The  Use  of  Saws — Forcing — Buckle — -Packing — -The 
Place  of  Coarse  and  Fine  Teeth — Holding  Work — Cutting  to  a  Line  78 

Chapter  IX. — Files. 

The  Forms  of  the  Teeth — Mode  of  Action — General  Plmployment  of 
Files — Sections — Derivations  of — Longitudinal  Forms — Degrees  of 
Coarseness  of  Cut  —  Terms  — -  Special  Files  —  Length  —  Special 
Handling  --------  93 

Chapter  X. — Milling  Cutters. 

More  Economical  than  Single-Edged  Tools — ^Multiplication  of  Edges — 
Discounted  by  Shallowness  of  Cutting — Rake — Durability — Spiral 
Twist — Period  of  Rest  during  Revolution — Question  of  Speeds — ■ 

How  Effected — Average  Rates — The  Work  of  each  Tooth — Neces¬ 
sity  of  Keeping  Edges  Sharp — Heavy  Feeds — Pitching  of  Teeth — 
Direction  of  Feeding — Varieties  in  forms  of  Cutters — Face  and 
Edge  Mills  —  Their  Proper  Spheres  —  Gang  Milling  —  Devices 
Adopted  in  Building  Up — Milling  Parallel  Grooves — The  Wear 
of  the  Mills — Combinations  of  Edges — Angular  Mills— The  Case 
of  Profiled  Forms  —  Examples  —  Profile  Milling  Compared  with 
Grinding — and  Planing  —  Profiling  Machines  —  Face  Mills  with 
Inserted  Teeth — Methods  of  Insertion — and  Securing — Advantages 
— Staggered  Teeth  in  Solid  Mills — Taper  Shank  Mills — Formed 
Mills — Lubrication  of  Cutters — Pickling  -  -  -  -  98 

Chapter  XL — Boring  Tools  for  Wood. 

The  Bradawl — The  Performance  of  the  Gimlet  Type — Its  Drawbacks — 

Bits,  and  Augers — Centre-Bit — Its  Unbalanced  Action — Expanding 
Centre-Bit — American  Screw  Bits — Forms  of  their  Cutters — Their 
Advantages — Counterboring — Improved  Braces 

b 


120 


X 


CONTENTS. 


Chapter  XII. — Boring  Tools  for  Metal.  page 

The  Drill — Variations  in  Flat  Drills— Its  Characteristics — Angles — 
Grinding— Twist  Drills — Early  Forms — Increase  Twist — Constant 
ditto — Cutting  Angles — Clearances — Effects  of  Grinding — The 
Point — Speed  of  Drills — Conditions  which  Affect  Speed — Lubrica¬ 
tion — Oil  Tubes — Shanks — Enlargement  of  Holes — Reamers — 

Boring  Tools — Pin  Drill  or  Counterbore  -  -  -  -  127 

Chapter  XIII.— Taps  and  Dies. 

Taps  and  Dies  a  Compromise — Difference  between  these,  and  Cutting 
with  Lead  Screw — Relation  between  a  Tap  and  its  Screwed  Hole — 

Initial  and  Final  Diameters — Sets  of  Taps — Operation  of — Reliev¬ 
ing — Cutting  Angles — Dies — Balance  of  Guidance  and  Cutting 
Power — Size  of  Master  Taps,  or  Hobs — Action  of  Dies — Notches — 

Guide  Screw  Stocks — Dies  in  Screw  Machines — Echolls  Taps  -  151 


SECTNV.— PERCUSSIVE,  AND  MOULDING  TOOLS. 

Chapter  XIV. — Punches,  Hammers,  and  Caulking  Tools. 

The  Punch — Spiral  ditto — Taper  of  Punch — Burr — Various  Punches — 

Drifts — Hammers — Varieties  of — Force  of  Blow — Mallets — Caulk¬ 
ing  Tools — for  Plates — for  Pipes  -  -  -  -  -  160 

Chapter  XV. — Moulding,  and  Modelling  Tools. 

Two  Great  Groups — That  which  is  Related  to  Percussive  Tools — 
Smiths’  Flatters,  Fullers,  and  Swages — Their  Co-relation  to  the 
Fibrous  Characters  of  the  Materials — Trowel  Group — Plasterers’ 

Tools — Moulders’ ditto — Cleaners — Sleekers  of  Various  Sections  -  168 

Chapter  XVI. — Miscellaneous  Tools,  and  Tool  Handles. 

Spanners — Wrenches — Ratchet  Braces — -Woodworkers’  Braces — Tap 
Wrenches — Pincers — Pliers — Tongs — Tool  Handles — Forms  Used 
for  Thrusting  —  for  the  Mallet  —  for  Turning  —  for  Planes  —  for 
Swinging — Summary  -  -  -  -  -  -  172 


SECTION  V.— HARDENING,  TEMPERING, 
GRINDING,  AND  SHARPENING. 

Chapter  XVH. — Hardening  and  Tempering. 

Distinction  between  Hardening  and  Tempering — Method  of  Heating — 
Precautions — Methods  of  Hardening — Quenching — Drawing  Tem¬ 
per — Annealing — Mechanical  Processes  -  -  •  -  182 


CONTENTS. 


XI 


Chapter  XVIII. — Tool  Grinding  and  Sharpening. 

Hand  Grinding  —  Variable  Results  of — Mechanical  Grinding  —  Due 
Largely  to  Emery  Wheels — Precision  of — Natural  Grindstones — 
Lack  of  Homogeneity — -Composition — Hardness  and  Softness — 
Glazing  —  Truing  —  Double  Grindstone  —  Speeds  of  Running — 
Mounting — Water — Comparison  between  Grindstones  and  Emery 
Wheels — Grading — Speeds  of  Truing — Forms  of  Wheels — Wet 
Grinding — Tool  Grinding — Tool  Grinders — Examples  of,  for  Hand 
Grinding — Grinding  Woodworkers’  Tools  by  Hand — Plane  Irons — 
Gouges  —  Sharpening  — Wire  Edge — Errors  in  Practice — Gouge 
Slips— Mechanical  Grinding — Examples  of  Machines  for  Single- 
edged  Tools — Sharpening  Reamers — Milling  Cutters,  &c.  - 


SECTION  FI— TOOTS  FOR  MEASUREMENT 

AND  TEST. 

Chapter  XIX. — Standards  of  Measurement. 

Definition — Rule  and  Gauge  Measurement — Standards — Temperature — 
Interchangeability — Limits  of  Accuracy — Early  English  Standards 
of  Measurement — Basis  of — Pratt  &  Whitney  Standards — Details — 
Line  Measures  and  End  Measures — Refined  Tests — Rules — Varied 
Forms  of — Use  and  Wear — Scales — Forms  of — Tapes — Rods 

Chapter  XX. — Squares,  Surface  Plates,  Levels,  Bevels, 

Protractors,  &c. 

Origination  of  Straight-edges — Care  of— Surface  Plates  —  Flexure — 
Plates  for  Standard  Reference — Large  Straight-edges — Winding 
Strips — Squares — Try  Squares — Testing  of — Method  of  Making — 
Combination  Squares — Centre  Squares — Bevels — Bevel  Protractors 
—  Scale  of  Chords — Set  Squares  —  Levels  —  Wear  of — Various 
Forms — Plumb  Bobs  ...... 

Chapter  XXL — Surface  Gauges,  or  Scribing  Blocks. 

The  Work  of  Lining-out — Preliminary  Checking  of  Leading  Dimen¬ 
sions — Centre  Lines — Cardinal  Dimensions —  The  Basis  of  a  Level 
Table — Packing  Up — Details — Scribing  Block — Its  Work — Illus¬ 
trations  of  its  Use — Differences  between  Good  and  Bad  Forms — 
Various  Kinds — Refinements  Described — Sciibers  - 

Chapter  XXII. — Compasses  and  Dividers. 

Distinction  between  Coarse  and  Fine  Adjustment — Stiffness  of  Legs — 
Modified  Forms — Combination  Types — Trammels — Examples — 
Centring  Balls — Parallel  Dividers  -  ... 


PAGE 


187 


215 


230 


247 


263 


xii  CONTENTS. 

Chapter  XXIII. — Calipers,  Vernier  Calipers,  and 
Related  Forms. 

Essentials  in  Calipers — -Proportions — Weight — Adjustability — External 
and  Internal  Types — Capacity  for  Adjustment,  How  Met — Special 
Forms — How  to  Use  Calipers — Examples — Compass  Calipers — 
Keyway  ditto — Vernier  Calipers — Principle  of  the  Vernier — Dif¬ 
ference  between  Vernier  and  Micrometer — Caliper  Rules — With 
and  without  Verniers  —  Examples  of  Vernier  Calipers  —  How  to 
Read — Examples  of  Various  Forms  .  .  .  . 

Chapter  XXIV. — Micrometer  Calipers. 

Principle  of  Design  —  Mechanism  of — Details  in  Combination  with 
Vernier — Taking  up  Wear — Various  Forms  Described — Horseshoe 
Type — Beam  Micrometer  Calipers — Screw  Thread  ditto— Gear 
Teeth  ditto  -------- 

Chapter  XXV. — Depth  Gauges  and  Rod  Gauges. 

Measuring  Depths,  and  Diameters — By  Rod  and  Rule — Applications 
of  Micrometer  and  Vernier  to — Forms  of  Depth  Gauges — Reading 
Dimensions — Refinements  in  Design — Combination  Form — Rod 
Gauges — Examples  ------- 

Chapter  XXVI.— Snap,  Cylindrical,  and  Limit  Gauges. 

Horseshoe  Calipers — Difference  between  Standard  and  Limit  Gauges — 
The  Newall  System  —  Provisions  against  Wear  —  Accuracy  of 
Cylindrical  Gauges — and  Horseshoe  ditto — Examples  of  Gauges — 
Plug  and  Ring — Snap  Gauges  .  -  -  .  . 

Chapter  XXVIL — Screw  Thread,  Wire,  and 
Reference  Gauges. 

Gauges  for  Grinding  and  Setting  Screw  Thread  Tools — Thread  Gauges 
— Combination  Forms — Reference  Gauges — Pipe  Threads — Gauges 
for  Holes  for  Screwing,  and  for  Keyways — Wire  Gauges  - 

Chapter  XXVIH. — Indicators  and  Templeting. 

Principle  of  Design — Examples — Relation  to  the  Surface  Gauges — 
Templeting — Templets  and  Jigs — Their  Preparation — Weight — 
Stamping — Metric  System  ------ 


FAGB 


271 


287 


300 


309 


317 


327 


INDEX  - 


334 


TOOLS  FOR  ENGINEERS  AND  WOODWORKERS. 


INTRODUCTION. 

A  General  Survey  of  Tools. 

The  Term  Tool  Defined — Distinction  between  a  Tool  and  a  Machine — -and 
an  Appliance — Instruments  for  Measurement  and  Test — Broad  Grouping 
— Machine-operated  Tools,  and  Modern  Manufacture — Percussive  Tools 
— Moulding  Tools — Interchangeable  System- — The  New  Steels. 

IT  is  necessary  to  have  a  clear  definition  of  the  meaning  of 
the  word  tool.  What  is  a  tool  ?  in  what  respect  is  it  dis¬ 
tinguished  from  a  machine,  an  appliance,  an  implement,  or 
an  instrument?  The  term  is  used  in  a  very  loose  fashion,  but 
the  scope  of  this  volume  must  be  restricted  to  the  legitimate 
meaning  of  the  word. 

On  first  thoughts,  it  might  seem  as  though  the  dictionary 
definition  were  correct — being  any  instrument  of  manual  opera¬ 
tion,  one  dependent  for  its  effect  on  the  strength  and  skill  of  the 
operator.  But,  though  that  would  hold  good  in  a  primary  sense, 
and  absolutely  so,  say  about  a  hundred  years  ago,  it  does  not  by 
any  means  cover  the  legitimate  meaning  of  the  term  to  day. 
Such  a  definition  would  exclude  all  the  vast  numbers  of  tools 
which  are  held  in  and  operated  by  machines,  all  of  which  are 
directly  related  to,  or  derived  from  hand  tools,  and,  in  some  cases, 
are  similar  to,  or  identical  with  the  latter. 

The  machines  themselves,  however,  do  not  come  under  the 
classification  of  tools,  though  this  term  is  commonly  and  loosely 
applied  to  them,  and  also,  and  more  correctly,  the  phrase 
machine-tools.  These  therefore  will  not  receive  any  treatment 
in  this  volume. 

A 


2 


TOOLS. 


The  distinction  between  a 'tool  and  an  appliance  is  also  to  be 
borne  in  mind.  Anything  by  which  the  progress  of  work  is 
facilitated  we  call  an  appliance,  or  in  some  forms,  a  templet,  or  a 
jig,  the  three  terms  denoting  different  objects.  Just  where  to 
draw  the  line  here  is  difficult.  A  spanner  is  a  tool,  but  though  a 
vice  may  be  considered  as  a  tool,  it  is  strictly  an  appliance,  since 
it  holds,  but  does  not  operate  on  work.  In  these  and  kindred 
matters,  the  limitations  of  a  volume  must  be  borne  in  mind  in 
making  selection,  and  so  only  those  articles  which  can  be  legiti¬ 
mately  classed  as  tools  will  receive  treatment. 

There  is  another  large  group  of  tools  which  are  also  termed 
instruments,  being  those  employed  for  marking  out,  and  in  the 
measurement  and  testing  of  work.  They  are  tools,  because 
employed  in  and  being  essential  to  the  conduct  of  manual  opera¬ 
tions.  The  growth  of,  and  the  increased  importance  of  these  in 
recent  years  has  been  of  a  phenomenal  character,  and  no  treatise 
on  tools  from  which  these  are  to  be  omitted  can  now  be  con¬ 
sidered  as  in  any  sense  complete. 

Having  defined  the  sense  in  which  we  propose  to  regard  tools, 
let  us  now  see  how  the  subject  most  naturally  divides  itself. 

First  we  have  the  two  broad  groups — of  tools ;  and  of  instru¬ 
ments  for  measurement.  The  first  includes  a  large  number  which 
we  can  classify  broadly  as  follows,  notwithstanding  that  overlap¬ 
ping  occurs  in  some  of  the  groups. 

Tools  which  act  by  cutting,  by  shearing,  by  scraping,  by 
abrasion,  by  detrusion,  by  percussion,  tools  which  operate  by 
moulding  on  plastic,  or  on  loose  materials,  and  those  of  the  lever 
class.  And  in  connection  with  all  except  the  last  two,  there  is 
the  question  of  the  maintenance  of  maximum  efficiency,  by 
hardening,  tempering,  and  grinding. 

Under  the  head  of  instruments  of  measurement  are  included 
tools  used  for  marking  lines,  straight  and  circular,  on  work,  for 
obtaining  the  geometrical  relations  of  such  lines,  and  for  producing 
centres.  These  constitute  several  large  groups.  Another  great 
class  which  includes  several  groups  is  employed  for  checking  and 
testing  the  accuracy  of  work  in  progress  and  when  completed. 
And  these  again  include  two  important  subdivisions — those  which 
are  employed  for  direct  measurement,  and  those  for  measurement 
by  the  sense  of  touch  or  contact,  e.g.,  rules,  and  gauges. 

Overlapping  occurs  in  these  groups,  as  in  many  cutting. 


INTRO  D  UCTION 


3 


shearing,  and  abrasive  tools,  in  detrusive  and  shearing  tools,  and 
in  those  used  for  measurement  and  test  by  contact,  combined  with 
direct  measurement. 

Tools  of  the  lever  class  include  spanners  and  clamps,  pincers 
and  pipe  wrenches,  tap  wrenches,  screwdrivers,  and  allied  forms. 

Percussive  tools  form  a  very  large  group,  for  almost  every 
trade  has  its  own  distinct  group  of  hammers.  Besides  there  are 
the  hammers  incorporated  with  machines. 

Moulding  tools  are  used  by  plasterers,  modellers,  and  iron  and 
brass  founders,  and  these  are  large  groups. 

There  is  also  the  distinctly  modern  aspect  of  the  study  of 
tools,  which  must  be  indicated,  because  it  looms  so  large  in  the 
practice  of  present-day  engineering.  The  substitution  of  the 
machine-operated  tool  for  the  hand  tool  has  been  follow'ed  and 
supplemented  and  modified  extensively  by  a  system  of  manu¬ 
facture  known  as  the  Interchangeable.  The  essential  difference 
between  this  system  and  the  older  one  is,  that  all  similar  pieces 
will  interchange  in  the  first,  and  that  they  will  not  in  the  second. 
That  is,  if  a  thousand  pieces  were  thrown  in  a  heap,  any  one 
picked  up  at  random  would  fit  at  once  in  its  position  in  any  one 
of  a  thousand  mechanisms  of  which  it  forms  a  part.  Little  know¬ 
ledge  of  machine  work  is  required  to  understand  that  perfect 
interchangeability  demands  a  very  fine  adherence  to  fixed  dimen¬ 
sions.  A  variation  of  only  a  few  thousandths  of  an  inch  makes 
all  the  difference  between  too  close  a  fit  and  one  too  loose.  Such 
fine  dimensions  are  worked  to  in  hand  operations  by  a  tedious  pro¬ 
cess  of  fitting,  of  mutual  adjustments,  of  trial  and  error.  In  this 
way  perfect  fitting  of  parts  can  be  effected.  But  the  important 
point  is  this,  that  much  more  than  a  close  mutual  fitting  of  parts 
is  required  if  pieces  are  to  interchange.  They  must  all  be  to 
exact  and  absolute  dimensions,  which  is  quite  another  condition. 
There  is  almost  an  infinite  'difference  between  the  mutual  fitting 
of  a  few  parts  and  of,  say,  a  thousand  similar  pieces,  the  cost  of 
which  would  be  excessive  if  done  by  hand-operated  tools.  The 
difference  is  that  between  shaping  pieces  to  exact  gauged  dimen¬ 
sions  in  machines,  and  their  correction  by  the  manual  skill  of 
the  fitter  after  the  work  of  the  machines  has  been  completed. 
Then  the  parts  are  mutually  fitted  only,  but  not  to  dimensions 
predetermined  to  some  minute  fractional  parts  of  an  inch  or 
millimetre. 


4 


TOOLS. 


The  difference  is  most  important  from  the  point  of  view  of 
shop  economies  and  of  competitive  manufacture.  To  put  the 
case  in  a  concrete  fashion,  suppose  that  small  arms,  sewing 
machines,  and  typewriting  machines  were  each  finished  by  the 
manual  skill  of  the  fitter,  instead  of  being  put  together  or 
“assembled,”  as  the  parts  come  from  the  machines.  The  cost 
would  not  only  be  enhanced  enormously,  but  whenever  a  part 
should  require  renewal,  the  entire  mechanism,  or  a  considerable 
portion  of  it,  would  have  to  be  sent  back  to  the  factory  to  be 
refitted. 

It  was  in  France  first  of  all,  in  the  manufacture  of  muskets, 
but  subsequently  in  America,  that  the  interchangeable  system 
received  its  early  development.  Machines  and  accessories,  jigs, 
templets,  and  special  tools  were  designed  at  great  cost,  and  with 
much  labour,  to  ensure  absolute  uniformity  in  the  dimensions  of 
similar  parts  independently  of  the  skilled  craftsman,  and  with 
corresponding  economy  of  labour  and  reduction  in  the  cost  of 
manufacture.  Milling  machines,  screw  machines,  and  the  turret 
lathe  were  early  employed  in  this  work.  The  system  reached  its 
highest  development  in  the  United  States,  and  from  thence  was 
imported  to  England,  being  applied  at  first  to  the  manufacture  of 
small  arms.  But  the  Americans  subsequently  adapted  the  system 
to  the  production  of  sewing  machines,  of  watches,  and  numbers  of 
small  articles,  and  then  lastly  into  the  work  of  machine  tool  making. 
Many  engineering  firms  in  England  and  Germany  have  adapted 
their  shop  systems  to  the  production  of  strictly  interchangeable 
parts.  It  requires  little  prescience  to  see  that  on  the  extent  to 
which  this  system  is  adopted,  the  vitality  and  permanence  of 
many  competitive  firms  will  depend. 

I’here  is  an  immense  difference  in  machine  manufacture 
carried  on  under  such  a  system  and  the  older  one.  In  the  latter, 
each  machine  is  the  product  of  high  manual  skill,  made  to  order 
and  singly,  each  part  being  produced  and  carried  singly  through 
all  the  departments,  and  subjected  in  the  process  of  putting 
together  to  innumerable  corrections  at  the  hands  of  the  skilled 
mechanic.  No  dimensions  are  gauged  precisely,  but  corrected 
to  fit  “  full  ”  or  “  bare,”  as  required  for  mutual  fitting. 

In  the  new  system,  machines  are  produced,  not  by  the  labour 
of  highly  skilled,  highly  paid  mechanics,  but  either  by  unskilled 
cheap  labour  or  by  skill  of  a  low  grade.  Such  close  accuracy  in 


INTRO  D  UCTION 


5 


absolute  dimensions,  produced  in  parts  in  large  quantities  at  a 
low  cost,  are  apparently  antagonistic  conditions.  They  are  not  so 
in  fact  in  modern  practice.  They  are  obtained  with  ease,  and 
with  variations  so  slight  that  fine  gauges  are  required  to  detect 
them.  Parts  are  made  an  “  easy  fit,”  a  “  tight  fit,”  a  “  driving 
fit,”  as  desired,  and,  out  of  thousands,  the  percentage  of  misfits  is 
very  small.  The  difference  between  the  old  and’  the  new,  the 
heterogeneous  and  the  uniform,  the  mutual  fitting  by  skilled 
labour,  and  the  absolute  fitting  to  gauge,  is  wholly  a  question  of 
machinery  of  an  automatic  or  semi-automatic  character.  The 
broad  contrast  between  these  machines  and  methods  and  those 
which  they  displace  is  this  :  The  provisions  for  cutting  to  the  re¬ 
quired  dimensions  are  embodied  in  the  machines  themselves, 
while  in  the  older  system  accuracy  depends  on  the  care  exercised 
by  the  attendant  in  checking  the  size  of  work  while  in  progress. 
The  movements  of  modern  machines  are  not  arrested  until  the 
work  is  finished,  and  the  product  is  then  removed  without  measur¬ 
ing  it  at  the  machine.  The  main  difference  is  therefore  that  due 
to  the  substitution  of  automatic  and  semi  automatic  action  and 
control  for  that  of  the  workman. 

Another,  the  latest  development  in  tools,  relates  to  the  material 
employed,  the  “  high  speed  steels,”  by  which  output  is  trebled  or 
quadrupled.  These  steels  . date  from  1900,  when  the  Taylor 
White  brand  was  exhibited  at  Paris.  Many  other  brands  are 
now  in  the  market,  and  the  remarkable  result  is  that  lathes  are 
being  re-designed  to  endure  the  stresses  imposed  by  the  new 
cutting  steels,  which  are  often  capable  of  removing  over  a  ton  of 
cuttings  in  a  day  of  nine  hours. 


CHAPTER  1. 

Tool  Angles. 

Knives  and  Razors — The  Chisel  Group — Planes — Chisels  for  Metal — Principles 
Underlying  Tool  Angles— Tool  Formation — A  Compromise — Lessons  from 
the  Chisel — Angles  Controlled  by  Characteristics  of  Materials — Shavings 
and  Chips — Action  of  the  Plane  Compared  with  Metal  Cutting  Tools — 
Lessons  Learned  from  Hand  Tools — Rigidity  of  Tools — Summary  of 
Practical  Results — No  Hard  and  Fast  Rules — The  Importance  of  Support 
Afforded  to  the  Work  and  the  Tools— and  of  Lubrication — Tools  that 
Embody  the  Chisel  Action — The  Scrape — Abrasion — Shearing — Detrusion 
— Tools  which  Occupy  an  Uncertain  Position. 

WE  will  now  endeavour  to  trace  rapidly  the  tool  angle 
principle  through  many  diverse  forms,  ranging  from 
the  keenest  cutting  tools  to  those  which  operate  by 
scraping  only. 

The  principle  on  which  the  forms  of  cutting  tools  are  based 
is  traceable  through  many,  and  on  first  thoughts  unrelated, 
types.  Tools  of  the  chisel  form  will  cut  anything  from  cork  and 
leather  to  the  tough  and  hard  steels.  The  saw  will  sever  wood, 
stone,  brass,  iron,  and  steel.  The  differences  are  simply  different 
applications  of  the  fundamental  principles  on  which  the  tools 
are  made. 

The  keenest  tools  are  the  knife  and  razor,  in  which  the  cutting 
angles  measure  a  few  degrees  only,  seldom  or  never  exceeding 
20°.  These  are  not  required  to  sever  or  shave  hard  substances, 
and  they  therefore  retain  their  edge  for  a  reasonably  long  period. 

The  next  increase  in  angle  occurs  in  the  chisels  and  cognate 
forms  for  cutting  soft  and  hard  woods.  The  grinding  angle  here 
is  increased  to  from  about  20°  to  25°,  and  we  have  our  first 
examples  of  a  sharpening  facet,  the  angle  of  which  with  the 
permanent  face  is  slightly  greater  than  the  grinding  angle.  This, 
however,  is  only  a  matter  of  convenience,  because  less  time  is 
occupied  in  sharpening  such  a  narrow  facet,  than  would  be  re¬ 
quired  for  sharpening  all  over  the  ground  bevel. 


TOOL  ANGLES. 


7 


Akin  to  the  chisels  in  degree  of  angle,  and  in  method  of 
sharpening  just  noted  are  the  gouges,  draw-knife,  hatchet,  axe, 
adze,  turning  chisels,  and  gouges,  carvers’  tools,  and  allied  forms. 
A  feature  which  all  these  have  in  common  is,  that  no  coercion  is 
exercised  upon  them,  save  that  of  the  workman’s  hands.  They 
can  lay  when  in  action  flat  against  the  work,  or  be  tilted,  and 
thrust,  or  driven  to  suit  the  shape  of  the  surface  of  the  piece 
operated  on,  and  the  object  which  the  workman  has  in  view. 
The  chief  distinction  between  the  tools  of  this  group  is  that  of 
operation  by  thrust,  as  in  the  true  chisels  and  gouges,  and  that 
by  percussion,  as  in  the  hatchet,  and  adze  group.  Here,  however, 
overlapping  occurs,  since  most  chisels  can  be  operated  either  by 
'hand  thrust,  or  be  struck  with  a  mallet. 

In  the  next,  and  an  important  group,  the  chisel  is  controlled 
by  the  guidance  of  a  stock  of  wood  or  metal,  and  becomes  a 
plane.  This  is  not  a  fanciful  distinction,  for  ordinary  chisels  are 
so  rigged  up  frequently  in  a  temporary  fashion,  in  a  wooden  block, 
for  a  special  and  temporary  duty. 

The  fixing  of  a  chisel  in  a  plane  stock  gives  rise  to  a  large 
range  of  possibilities,  as  a  study  of  the  immense  range  of  the  plane 
group  reveals.  There  are  several  scores  of  distinct  types  of  planes, 
and  made  in  different  sizes.  Most  are  used  for  producing  plane 
surfaces,  but  large  numbers,  have  profiled  forms,  to  reproduce  the 
opposite  sections,  some  sections  being  simple  regular  curves, 
others  profiled,  and  moulded.  Some  have  double  irons,  that  is 
a  break,  or  top  iron  in  addition  to  the  cutting  iron.  But  from 
the  point  of  view  of  angle,  the  principal  thing  to  note  is  that  the 
controlling  face  is  no  longer  the  face  of  the  plane  iron  itself,  but 
that  of  the  stock  in  which  it  is  rigidly  embraced,  and  the  iron  does 
not  lie  flatwise  on  the  work.  Such  being  the  case,  we  find  great 
variations  in  the  angles  at  which  the  irons  are  set  in  their  stocks, 
the  practical  advantage  of  which  is  that  the  planes  can  be  accom¬ 
modated  to  the  cutting  of  diverse  materials,  hard  and  soft,  harsh, 
stringy  and  knotty,  or  mild  and  sweet.  In  most  cases  the  bevel 
is  set  downwards,  or  next  the  face,  bringing  the  sharpened  facet 
nearly  into  line  with  the  surface  of  the  work  being  cut,  giving  an 
“angle  of  relief.”  In  others  the  flat  face  is  set  downwards,  and 
the  iron  is  then  fixed  at  a  very  low  angle  in  the  stock. 

Following  the  chisel  form  into  the  working  of  metals — the 
softer  kinds,  as  lead  and  copper,  being  excluded — there  is  no 


8 


TOOLS. 


1 

example  of  a  hand-operated  chisel  being  used  by  simple  thrust. 
Either  the  tools  of  this  type  are  used  percussively,  as  in  the  cold 
chisels,  or  if  thrust,  or  drawn,  it  is  done  by  the  power  of  a 
machine.  In  each  case  the  difference  between  metal,  and  timber 
and  kindred  soft  materials  is  the  reason  for  alterations  in  the 
cutting  angles.  These  angles  are  much  more  obtuse  for  metal 
cutting,  and  they  increase  with  the  growing  toughness  and  hard¬ 
ness  of  the  metals,  and  depending  also  on  whether  a  given 
material  is  being  cut  cold  or  hot.  The  percussive  tools  afford 
examples  of  this  difference,  the  hot-sett  of  the  smith  and  boiler¬ 
maker  having  keener  angles  than  the  cold-sett. 

The  principles  underlying  the  angle  of  a  cutting  tool  are 
these :  The  edge  formed  by  the  meeting  of  the  upper  and  lower 
facets  must  be  sufficiently  keen — that  is,  must  possess  sufficient 
wedge  formation — to  penetrate  and  sever  the  material ;  it  must 
also  be  strong  enough  to  retain  its  keenness  of  edge  with  reason¬ 
able  permanence,  without  the  need  of  frequent  regrinding.  The 
friction  between  the  work  and  the  portion  of  the  tool  adjacent  to 
the  edge  must  be  reduced  as  much  as  practicable,  and  so,  too, 
must  the  friction  between  the  severed  chip  and  the  face  against 
which  it  comes  in  contact.  The  result  is  that  tool  formation  is 
always  a  compromise,  a  balancing  of  conditions : — a  keen  cutting 
angle  and  reduction  of  friction  being  opposed  to  the  strength  and 
permanence  of  the  cutting  edge.  Thus  in  Fig.  6i,  p.  58,  which 
represents  in  profile  a  typical  roughing  tool  suitable  alike  for 
turning  and  planing,  shaping  or  slotting,  it  will  be  observed  that 
the  tool  faces  are  all  included  a  good  way  within  90°.  If  a  tool 
filled  up  the  angle  of  90°  it  would  not  cut  at  all,  but  only  scrape ; 
nor  would  it  have  any  clearance. 

The  proper  starting  point  from  which  to  determine  the  shape 
of  a  tool  is  the  angle  of  clearance  a,  which  varies  in  practice  from 
3°  to  15°  or  even  20°.  5°  should  be  sufficient  in  any  tool,  because 

that  affords  just  enough  clearance  to  prevent  friction  between 
the  face  of  the  tool  and  the  surface  of  the  work  next  it,  and  the 
less  the  amount  given,  the  more  permanent,  of  course,  is  the 
edge,  because  it  is  well  supported  by  the  mass  of  metal  that  backs 
it  up.  In  some  tool  grinders  10°  is  a  standard  clearance  angle, 
and  it  is  probably  a  general  average.  One  reason  why  very  small 
clearance  angles  often  exist  is,  that  in  hand-grinding,  men  will  just 
touch  the  tool  near  the  edges  instead  of  grinding  down  the  entire 


TOOL  ANGLES. 


9 


face,  and  this  tends  to  thicken  the  edge,  just  as  a  woodworker’s 
chisel  becomes  thickened  by  sharpening  a  small  facet,  instead  of 
rubbing  across  the  whole  bevel  at  which  it  leaves  the  grindstone. 
I'here  is  reason  for  this,  but  none  for  grinding  a  narrow  facet  only. 

A  great  deal  can  be  learned  about  these  tool  angles  from  the 
common  chisel,  and  planes  of  the  woodworker,  operated  in  good 
and  bad  order,  and  on  soft  and  hard  wood,  since  they  are  cousins- 
german  to  the  tools  of  the  metal-turner.  A  much  keener  cutting 
angle  on  a  chisel  can  be  adopted  than  on  the  iron-turner’s  tool, 
simply  because  wood  is  softer  than  metal.  The  chisel  has  its 
angle  of  top  rake,  up  which  the  shaving  or  chip  curls  (Fig.  lo, 
p.  26).  When  the  cutting  angle  of  the  chisel  becomes  thickened 
by  repeated  re-sharpenings,  greatly  increased  force  is  required 
behind  it  to  enable  it  to  penetrate  the  wood.  And  a  chi.sel  ground 
and  sharpened  very  keenly,  cutting  pine  easily,  will  have  its  edge 
turned  over  against  very  hard  wood,  or  its  edge  will  sometimes 
even  become  notched  and  fractured,  indicating  the  necessity  for  a 
slight  increase  in  cutting  angle.  There  is  no  front  rake  in  the 
chisel ;  but,  in  fact,  a  workman  usually  tips  the  tool  a  very  minute 
amount  in  taking  a  paring  cut,  and  so  intuitively  gives  a  little  front 
rake  for  easier  working. 

The  angle  b  in  Fig.  61,  p.  58,  which  is  that  of  top  rake, 
governs  both  the  incisive  action  of  the  tool,  and  the  amount  of 
freedom  of  movement  of  the  severed  chip,  while  the  angle  c — the 
tool  angle — -determines  the  strength  of  the  tool  and  its  perma¬ 
nence.  The  greater  the  slope  of  the  top  face  the  better  for  cutting 
fibrous  metals,  for  reasons  to  be  noted  directly ;  but  too  much 
slope  causes  the  tool  to  dig  in,  especially  into  crystalline  metals 
and  alloys.  But  the  slope  cannot  be  increased  indefinitely, 
because  the  angle  c  would  be  reduced  too  much,  with  resulting 
weakening  of  the  tool  edge,  which  would  be  impaired  rapidly. 
'I'o  realise  these  points  it  is  only  necessary  to  compare  the  razor, 
or  newly-ground  chisel  for  wood,  with  a  tool  angle  of,  say,  about 
15°,  and  a  tool  for  cutting  hard  steel  with  an  angle  of,  say,  80°. 
Average  tool  angles  c,  for  average  wrought  iron,  cast  iron,  and 
gun  metal  are  50”,  65°,  80°,  or  90“  respectively.  The  angles  of 
top  rake  b,  just  now  referred  to,  will  range  from  35°  to  40°  for 
wrought  iron,  20°  to  25°  for  cast,  and  10°  to  zero  for  gun  metal. 
But  these  can  only  be  accepted  as  fair  averages,  though  for  con¬ 
venience  in  shop  systems,  where  grinding  is  done  to  gauge,  it  is 


lO 


TOOLS. 


desirable  and  usual  to  settle  certain  angles  and  adhere  to  them. 
It  is  better  on  the  whole  as  regards  results,  because  it  favours  the 
use  of  tool  grinders  and  gauges,  and  of  some  kinds  of  tool-holders. 

The  materials  operated  on  by  tools  are  hard,  and  soft,  tough, 
and  brittle,  fibrous,  and  crystalline.  Each  occurs  in  extreme 
forms,  and  in  a  large  range  of  intermediate  grades.  The  varia¬ 
tions  in  the  character  of  these  materials  help  largely  to  explain 
the  action  of  the  tools  of  different  classes.  Comparing  at  extremes, 
soft  wood,  or  leather,  and  hard,  or  tough  steel,  or  brittle  cast  iron, 
it  would  seem  almost  incredible  that  tools  formed  on  identical 
principles  should  be  capable  of  cutting  these  strongly  contrasted 
substances. 

The  thickening  of  tool  angles,  therefore,  cannot  be  considered 
alone,  since  it  is  related  to  the  fibrous,  crystalline,  or  other  char¬ 
acteristics  of  the  numerous  and  varied  qualities  of  metals  and 
alloys,  and  is  controlled  also  by  the  angle  of  the  cutting,  and  relief 
faces  of  the  tool  between  which  it  is  included. 

A  wide  angle  is  a  very  different  thing  from  bluntness  of 
edge.  An  edge  must  be  keen  and  sharp  for  severing  metal, 
as  for  wood,  but  in  order  that  the  edge  shall  retain  its  keenness 
for  a  reasonable  time,  it  must  be  backed  up  by  sufficient  metal ; 
in  other  words,  by  a  wide  tool  angle.  This  is  the  principle 
which  underlies  the  formation  of  the  various  metal-cutting  tools 
of  the  chisel  type,  as  will  be  explained  in  their  proper  sections. 
Other  requirements  have  to  be  fulfilled,  of  course,  such  as  the 
power  necessary  to  sever  the  metal,  dependent  largely  on 
whether  the  material  is  removed  in  the  form  of  shavings,  or  chips. 

It  is  an  axiom  that  if  the  severance  of  metal  is  to  be  effected 
with  the  minimum  of  power,  then  the  more  nearly  the  portion 
removed  approximates  in  length  to -the  surface  from  which  it 
was  taken,  and  the  larger  and  longer  the  shaving,  or  the  longer, 
and  less  broken  up  the  chips  are,  the  more  nearly  will  this  con¬ 
dition  be  fulfilled. 

The  distinction  being  shavings  and  chips  is  closely  related  not 
only  to  the  nature  of  the  material  operated  on,  but  also  to  the 
forms  of  the  tools,  and  the  various  conditions  under  which  they 
are  used.  To  render  this  clearly  understood  by  workers  in  wood, 
and  in  metal,  the  action  of  the  plane  iron  can  be  compared  with 
that  of  the  tools  of  the  iron-turner,  and  their  cognate  forms  used 
on  planer,  or  shaper. 


TOOL  AJVGLES. 


1 1 

Take  two  planes  exactly  alike  with  regard  to  the  angles  at  which 
the  irons  are  set  in  the  stock,  and  sharpened  exactly  alike,  the 
only  difference  being  that  one  has  a  single  iron — the  cutting  one ; 
and  that  the  other  has  two — the  cutting  iron,  and  the  back,  or 
top  iron.  The  first  will  throw  off  rough  shavings,  and  leave 
a  roughly  planed  surface ;  the  second  will,  if  the  top  iron  is  set 
close  down  to  the  edge  of  the  cutting  iron,  produce  silky  shavings, 
of  an  even  thickness,  and  leave  a  smooth  surface.  And  in  pro¬ 
portion  to  the  hardness,  harshness,  cross  grain,  knottiness  of  the 
timber  operated  on,  will  these  differences  be  in  stronger  contrast. 
In  fact,  in  the  extreme  conditions  of  hardness,  &c.,  the  use  of  a 
single  iron  is  impossible,  the  case  of  certain  iron-stock  planes 
excepted. 

The  explanation  of  the  difference  is  that  the  action  of  the  top 
iron  is  coercive,  that  it  bends  the  shaving  over,  and  by  causing 
it  to  turn,  and  curve,  lessens  the  tendency  of  the  cutting  iron 
to  tear  or  split  the  wood  in  wedgelike  fashion.  Putting  it  in 
another  way,  it  resembles  the  difference  between  the  combined 
wedging  and  splitting  action  of  the  axe,  or  adze,  and  the  paring 
action  of  the  chisel. 

In  the  metal-turner’s  tools,  we  have  the  turning  over  of  the 
shavings  cut  from  those  materials  that  are  capable  of  bending, 
as  the  mild  steels,  wrought  iron  and  copper,  and  in  a  lesser 
degree  in  the  softer  qualities  of  cast  irons.  It  is  in  order  to  permit 
of  this,  that  top  rake  is  imparted  to  the  roughing,  and  to  many  of 
the  finishing  tools.  A  larger  angle  of  top  rake  would  be  given 
than  is  the  practice,  but  for  the  fact  that  the  tool  would  be 
weakened  thereby.  In  theory  the  nearer  the  top  face  approaches 
the  tangent  to  the  work,  the  better  for  cutting.  But  as  a  wide 
angle — the  tool  angle — must  be  included  between  the  top  face  and 
the  front  clearance  angle,  this  limits  the  degree  of  .slope  which 
can  be  imparted  to  the  top  face. 

The  reason  why  greater  slope  is  necessary  for  cutting  fibrous 
metals  like  wrought  iron,  and  the  tougher  steels,  than  for  cast 
iron  and  brass,  is  that  continuous  shavings  come  off  from  the 
former,  and  chips,  that  break  up  instantly,  from  the  latter.  The 
shavings  grind  hard,  and  are  curled  against  the  top  face  of  the  tool, 
while  the  chips  fall  away  directly.  The  more  slope  that  can  be 
given,  therefore,  to  the  tool  face  in  the  first  instance,  the  better, 
while  it  is  a  matter  of  less  importance  in  the  latter.  This  accounts 


12 


TOOLS. 


for  the  common  practice  of  turning  brass  with  a  scraping  tool. 
The  small  chips  fly  off  at  once.  But,  all  the  same,  it  is  better 
when  roughing  down  brass  to  use  a  tool  with  some  top  rake. 
And,  generally,  the  tougher  the  material,  the  greater  in  reason' 
should  be  the  slope  of  the  top  face  of  the  tool,  in  order  to  permit 
the  cuttings  to  roll  off  more  easily. 

This  is  the  explanation  of  the  yards  of  shavings  that  are  readily 
cut  off  unbroken  from  these  materials.  If  there  were  no  top 
rake,  shavings  would  not  be  produced,  but  broken  chips.  And 
when  top  rake  is  insufficient  in  amount,  though  the  fibrous 
character  of  the  material  may  ensure  cohesion,  sufficient  to  prevent 
the  shavings  from  breaking  into  chips,  yet  they  will  be  curled 
round  into  smaller,  shorter,  tighter  spirals. 

The  test  therefore  of  a  true  incisive  tool  having  sufficient  top 
rake  is  the  production  of  large  shavings  of  great  length,  and  in 
the  case  of  cast  iron,  where  long  shavings  are  impossible,  the  less  of 
break  there  is  in  the  chips,  and  the  less  sliding  of  the  layers  over  one 
another,  is  the  test  of  a  proper  amount  of  top  rake.  No  shaving 
ever  made  in  fibrous  metals,  measures,  if  straightened  out,  the  full 
length  of  the  surface  from  which  it  is  severed,  testifying  to  the  fact 
that  some  crushing  action  always  takes  place. 

In  order  to  the  better  understanding  of  the  angles  of  clear¬ 
ance,  and  top  rake,  we  take  a  hand  tool,  which  may  be  a  graver. 


or  a  roughing,  or  finishing 
tool  made  of  triangular,  or 
square  bar.  Such  a  tool 
becomes  either  a  cutting 
instrument,  or  a  scrape  ac¬ 
cording  to  the  way  in  which 
it  is  presented  to  the  work  ; 
the  tool  angle  alone  does  not 
change.  In  Fig.  i  the  tool  is 
scraping,  in  Fig.  2  it  is  cutting. 


Fig.  I. 


Fig.  2. 


But  while  in  Fig.  i  the  angle  of  relief  is  so  large  that  the  tool  edge 
will  soon  be  lost,  in  Fig.  2  it  is  just  right  for  almost  any  material. 

A  safe  way,  therefore,  to  go  to  work  is  this.  Settle  a  minimum 
angle  of  front  clearance,  which  may  be  as  low  as  5°  and  need 
not  exceed  10°.  Then  make  the  top  angle,  or  top  rake,  as  large 
as  is  found  consistent  with  durability,  and  easy  cutting  of  the 
shavings.  In  other  words,  give  as  much  of  incisive  angle,  and 


TOOL  ANGLES. 


13 


chisel-like  action,  as  the  tool  will  endure,  with  permanence  of  shape. 
A  mean  can  thus  be  struck,  and  embodied  in  tool-holders,  and  in 
settings  for  grinding  in  shop  systems.  All  the  experimenting  and 
theory  in  the  world  will  not  get  beyond  these  simple  rules. 

There  is  another  aspect  of  this  subject  to  which  attention  should 
be  given.  Returning  to  the  plane  iron,  the  rigidity  produced  by  the 
screwing  down  of  the  top  iron  is  as  important  a  factor  as  its  bend¬ 
ing  of  the  shaving.  This  belief  is  borne  out  by  the  fact  that  any¬ 
thing  which  diminishes  chatter  produces  better  shavings,  and 
leaves  better  cut  surfaces.  An  iron  plane  works  better  than  a 
wooden  one,  because  its  mass  absorbs  chatter;  many  iron-stocked 
planes  have  single  irons  which  could  not  work  so  sweetly  in  wooden 
stocks.  Also  the  closer  the  top  iron  is  brought  down  to  the 
edge  of  the  cutting  iron,  the  less  the  chatter.  Again,  an  iron 
that  beds  best  on  its  stock,  and  that  is  secured  best,  works  sweet¬ 
est,  i.e.,  with  less  chatter.  So  that  the  function  of  the  top  iron  is 
just  as  much  that  of  preventing  or  lessening  vibration,  as  that  of 
bending  the  shaving. 

In  metal-turning  tools  also,  we  know  that  the  more  rigidly  the 
tools  are  held,  and  the  closer  they  are  supported  to  the  work,  the 
less  do  they  chatter,  and  the  better  is  the  cutting  done.  This  is 
exemplified  in  many  ways ;  in  tools  gripped  in  the  slide  rest,  some 
with  little  overhang,  and  some  with  an  excessive  amount,  in  tools 
gripped  in  holders,  in  overhanging  boring  tools  held  in  the  rest, 
and  in  bars,  and  in  boring  heads.  The  better  the  support  afforded, 
the  less  chatter,  and  the  sweeter,  and  smoother,  and  heavier  the 
cutting  possible. 

Tools  of  high  quality  have  been  used  since  the  days  of  the 
Pyramid  builders ;  and  even  long  antecedent  to  that,  the  first  flint 
chips  were  true  cutting  tools,  the  shapes  of  which  embodied  the 
same  elementary  principles  of  formation  as  the  chisels  and  gouges 
used  to-day.  But  during  those  thousands  of  intervening  years  no 
exact  science  of  tools  has  been  formulated,  and  so  a  great  deal  of 
what  some  would  term  empiricism  still  rules  in  the  shops.  There 
are  no  exact  angles  of  cutting  tools,  and  no  exact  formations  of  tool 
edges,  of  which  one  can  say,  confidently  ;  “  These  are  the  best,  and 
every  departure  therefrom  is  an  error  in  practice.”  It  would  seem 
desirable  in  these  days  of  formuUe  to  be  able  to  put  the  problem 
of  tool  edges  into  a  nutshell ;  but  neither  the  writers  on  the 
subject,  nor  the  practical  men  in  the  shops  have  yet  accomplished 


14 


TOOLS. 


this.  Either  would  have  done  it  if  the  task  had  been  easy ,  but 
the  difficulties  have  been  too  great. 

It  is  very  easy  to  state  the  principles  which  underlie  the  forma¬ 
tion  of  cutting  tools — no  one  calls  these  in  question.  In  the  whole 
range,  from  the  razor,  with  a  cutting  angle  of,  say,  15°,  to  those  for 
cutting  cast  iron  and  steel  with  angles  of,  say,  60°  or  80°,  we  find 
that  two  matters  have  to  be  balanced,  one  of  which  compromises 
the  other — the  maintenance  of  the  maximum  keenness  of  the 
cutting  angle,  with  the  maximum  endurance  or  capacity  of  the  tool 
to  resist  the  loss  of  its  edge.  That  remains  the  fundamental  fact 
or  principle — the  basis  which  underlies  the  essential  design  of  all 
cutting  tools  whatsoever.  Going  a  step  farther,  it  is  also  true  that 
as  a  rule  the  softer  the  material  operated  on,  the  more  acute  can 
the  angles  of  the  facets  of  the  tool  be  made ;  while,  on  the  contrary, 
the  harder  the  material  the  more  obtuse  must  they  be.  But  exactly 
what  the  angle  should  be  to  suit  best  any  given  material,  apart  from 
trial  or  previous  experience,  has  not  yet  been  made  the  subject 
.  of  exact  determination. 

Quite  as  chaotic  is  the  problem  of  what  is  termed  the  angle  of 
presentation,  and  that  of  relief  or  clearance.  We  are  prepared  to 
find  a  considerable  range  possible  to  the  latter,  though  there  seems 
no  good  reason  why  it  should  ever  exceed  from  5°  to  6°.  But  it 
very  often  does,  and  without  any  apparent  detriment  to  the  per¬ 
manence  of  the  tool  edge.  With  regard  to  the  angle  of  presenta¬ 
tion,  it  seems  as  if  some  precise  angle  ought  to  be  better  than  any 
others  for  a  given  class  of  material,  both  for  effecting  severance, 
and  for  clearing  the  stuff  severed  with  the  minimum  of  friction. 
Yet  that  has  not  been  fixed,  for  those  angles  range  within 
several  degrees  without  appearing  to  be  inconsistent  with  good 
practice. 

The  case  'stands  something  like  this  to-day.  Men  work  in 
grooves.  They  find  certain  results  follow  from  the  use  of  certain 
tool  angles,  and  then  they  lay  down  theories  which  harmonise 
with  those  results,  and  think  that  in  so  doing  they  have  formulated 
rules  of  universal  application.  That  is  just  where  the  error  comes 
in ;  for  the  rule  deduced,  if  universally  applied,  does  not  square 
with  universal  facts.  For  there  are  several  conditions  which 
exercise  important  influences  on  the  operation  of  cutting  tools,  chief 
among  which  are  differences  in  the  physical  characteristics  of 
materials  nominally  the  same,  the  effect  of  cutting  speeds  and 


TOOL  ANGLES. 


^5 


feeds,  the  support  afforded  to  the  tool,  and,  last,  and  equally  impor¬ 
tant  at  least  with  the  others,  lubrication. 

With  regard  to  the  first  set  of  conditions,  the  denominations — 
cast  iron,  wrought  iron,  steel,  and  brass — tell  but  little  of  the 
physical  characteristics  of  the  materials  which  are  classified  by 
those  names.  Cast  iron  may  have  a  toughness  and  hardness 
closely  approximating  to  that  of  the  quality  of  cast  steel,  or  it  may 
flake  off  in  soft  powdery  chips.  Obviously  the  tool  best  suited  for 
dealing  with  one  quality  cannot  be  the  best  for  the  other.  The 
same  remark  applies  to  forgings  in  different  qualities  of  steel, 
and  in  a  lesser  degree  to  wrought  .iron.  The  gun-metals  and 
brasses  again  range  from  tough,  hard,  and  crystalline  to  soft 
qualities. 

Taking  next  the  question  of  speed,  a  high  rate  of  cutting  speed 
will  rapidly  grind  away  a  thin  keen  tool-edge,  and,  therefore,  rate, 
and  depth  of  cut  are  both  limited  by  the  durability  of  the  tool 
itself.  But  lubricate  in  quantity,  and  the  edge  endures  even  at  a 
higher  speed,  and  takes  a  deeper  cut  or  coarser  feed  than  with¬ 
out  the  lubricant.  In  extreme  instances  we  find  examples  of  rapid 
and  efficient  tooling  done  with  cutting  angles  that  appear  incorrect 
in  theory,  results  superior  to  those  obtained  with  correctly  formed 
tools  and  ordinary  methods. 

AVe  find,  therefore,  that  the  subject  of  the  angles  of  tools  has 
in  some  degree  been  permitted  to  obscure  other  matters  which  are 
of  equal  importance.  This  does  not  'imply  that  these  angles 
should  receive  less  attention,  but  that  the  other  conditions  should 
have  more.  Lubrication  appears  to  be  of  equal  value  with  angles, 
yet  until  recently  it  has  not  been  studied  and  applied  with  one 
hundredth  part  of  the  interest  and  care  that  has  been  devoted  to 
the  former. 

A  secondary  condition  also  which  is  studied  to  a  greater  extent 
now  than  formerly,  is  that  of  affording  support  to  the  work  in 
opposition  to  the  action  of  the  tool.  In  older  shop  practice  if  this 
was  ill  supported,  the  feed  of  the  tool  was  generally  lessened,  so 
reducing  its  efficiency.  Now,  one  of  the  most  striking  differences 
between  the  design  of  the  lathe  tools  of  a  few  years  since,  and 
those  of  the  most  advanced  practice  of  the  present  day,  lies  less  in 
tool  forms  and  angles  than  in  the  better  support  afforded,  in  con¬ 
junction  with  more  complete  lubrication.  We  have  probably  not 
learned  much  more  about  tool  angles  than  Willis  and  Babbage 


i6 


TOOLS. 


taught ;  but  we  are  better  acquainted  with  other  conditions  that 
also  make  for  efficiency. 

In  the  ordinary  lathe  there  is  but  one  way  of  opposing  the 
action  of  the  cutting-tool — that,  namely,  of  a  steady  acting  in  the 
rear,  or  one  encircling  the  work  adjacent  to  the  tool.  Some  few 
heavy  lathes  embody  the  duple.x  system,  in  which  one  tool  is 
diametrically  opposed  to  the  other — an  excellent  device,  but  one 
which  is  obviously  limited  in  its  application.  The  balancing  of 
cutting  forces,  or  of  rendering  support  to  the  work  is  now  exten¬ 
sively  carried  out  in  the  various  box  tools  fitted  to  modern  turret 
lathes,  and  in  the  hollow  mills  (Fig.  3)  and  kindred  forms.  The 
adoption  of  the  same  principle  in  screwing-dies  renders  their  opera¬ 
tion  so  much  more  rapid  than  that  of  cutting  a  thread  in  a  lathe 
with  a  single  pointed  tool. 


It  is  not  necessary  for  high  efficiency  that  forces  should  be 
balanced  by  the  cutting  tools  themselves.  If  adequate  resistance 
is  offered  to  the  action  of  a  single  tool,  that  is  sufficient.  To  fit 
two  or  more  tools  for  simultaneous  action  introduces  complica¬ 
tions  which  would  for  some  work  involve  a  too  great  expense.  It 
is  very  often  quite  enough  to  use  a  single  tool,  and  to  support  the 
work  behind  it  with  a  vee’d  guide  (Fig.  4)  following 
immediately  after  the  cut, — our  old  friend  the  lathe- 
steady  in  a  new  and  simpler  guise.  Supported 
thus,  depths  of  cut  of  from  ^  in.  to  f  in.  are 
constantly  being  taken  with  fine  feeds. 

In  the  box  the  support  is  often  more  rigid 
than  that  of  the  lathe-steady,  because  both  tool 
and  guide  are  carried  as  closely  together  as  pos¬ 
sible  in  the  very  stiff  box  attached  to  the  turret, 
and  from  which  all  possibility  of  spring  is  eliminated.  The 
tools  used  for  roughing  are  similar  to  those  in  the  ordinary  lathe 
work,  or  they  resemble  what  are  termed  “  knife  tools  ”  (Fig.  5), 


Fig.  5- 


TOOL  ANGLES. 


17 


and  the  box  is  their  tool-holder.  A  small  angle  of  clearance  is 
given  and  an  average  cutting  angle,  and  these  tools  are  capable 
of  removing  broad  shavings.  In  the  most  complete  boxes,  two, 
and  sometimes  three  tools  operate  either  simultaneously  or  suc¬ 
cessively  on  one  piece,  each  tool  having  its  own  vee-support  at 
the  opposite  side. 

The  slogging  done  with  these  tools  could  not  be  accomplished 
without  the  assistance  of  floods  of  lubricant.  While  writers  on 
tools  have  long  emphasised  the  evil  of  the  rapid  generation  of 
heat,  and  pointed  out  the  obvious  advantages  which  would  result 
from  an  ample  supply  of  cooling  fluid,  the  problem  has  been 
solved  by  the  adoption  of  entirely  new  methods,  familiar  to  many 
because  they  are  now  adopted  in  many  of  the  more  advanced 
English  shops.  They  differ  from  the  drip-can  device  in  the  im¬ 
mensely  greater  volume  of  lubricant,  pumped  in  such  quantity  that 
it  partially  or  wholly  conceals  the  work  being  cut  from  observation. 
In  the  case  of  reamers  or  boring-tools  it  is  pumped  into  the  interior 
of  the  reamer,  or  into  the  recess  being  bored.  Instead  of  soapy 
water  being  employed,  lard-oil  is  frequently  used,  which,  though 
costly,  is  yet  economical,  because  employed  over  and  over  again. 

The  secret  of  heavy  cutting  must  therefore  be  credited  to 
lubrication  and  tool  support  equally  with  tool  angles.  Until 
within  recent  years  machinists  knew  little  of  the  possibilities  that 
were  hidden  in  these.  Now  they  boldly  attack  large  breadths  of 
metal.  Taken  in  conjunction  with  good  average  angles  the  tools 
feed  with  avidity,  and  that  they  are  not  being  unduly  stressed  is 
apparent  from  the  fact  that  they  often  retain  their  edges  for  several 
days,  even  though  in  constant  use,  without  regrinding,  showing  in 
this  respect  also  a  far  better  record  than  common  tools  in  lathe 
and  planer  operated  under  common  conditions.  This  could  not 
be  the  case  but  for  the  aids  afforded  by  lubrication  and  support, 
however  correctly  the  edges  might  be  ground. 

It  is  now  well  understood  that  lubrication  can  only  reach  its 
fullest  efflciency  when  it  is  proportioned  to  the  heaviness  of  the 
duty  of  the  cutting  tool.  The  harder  a  tool  is  worked,  the  more 
profuse  must  it  be.  The  fluid  used  must  also  be  supplied  right  at 
the  edge  of  the  tool,  and  be  allowed  to  flow  away  at  once,  to  be 
replaced  continually  by  fresh,  cool  liquid.  The  broader  the  work, 
and  the  more  rapid  the  feed,  the  more  heavily  are  the  cooling 
properties  of  the  liquid  taxed. 

B 


i8 


TOOLS. 


The  advantages  of  lubrication  are  so  great  that  in  modern 
practice  cast  metals  are  sometimes  so  treated,  brass  quite 
commonly,  and  occasionally  even  cast  iron,  both  of  which  are 
tooled  dry  in  the  ordinary  practice  of  the  lathe  and  machine  shop. 

In  conclusion,  the  balancing  of  cutting  forces,  the  giving  ample 
support  to  work  and  to  tools,  and  floods  of  liquid  are  the  later 
features  noticeable  in  the  operation  of  cutting  tools,  and  these  to 
some  extent  diminish  the  importance  which  has  been  hitherto 
accorded  to  exact  tool  angles.  The  necessity  of  observing  good 
average  angles  for  given  conditions  of  working  is  not  neglected; 
but  the  point  is  that  this  is  only  one  factor  in  the  economies 
and  efficiencies  of  cutting  tools,  and  that  others  which  are  of  equal 
value  are  those  noted  above. 

A  large  number  of  tools  that  bear  no  external  resemblance  to 
the  chisel,  and  the  tools  of  this  group  used  for  cutting  by  lineal 
movements,  possess  the  chisel  action.  But  so  many  lie  on  the 
border  line  between  cutting,  scraping,  abrasion,  and  shearing  that 
we  had  better  touch  on  these  methods  of  operation  at  this  stage. 

When  the  working  face,  or  the  top  face  of  a  tool  stands  at  an 
angle  of  90°  or  more  with  the  face  on  which  it  is  operating,  or 
with  the  tangent  to  that  face  in  circular  work,  it  is  not  a  cutting 
tool,  but  a  scrape.  Such  tools  are  frequently  used  for  turning 
brass,  and  for  finishing  smoothly  the  surfaces  of  iron  and  steel, 
which  have  been  previously  roughed  out  with  cutting  tools.  The 
cabinetmaker’s  toothing  plane  is  an  example  of  a  scrape  for  wood. 
Final  correction,  and  finish -frosting  is  put  on  metal  work  by 
scrapers,  which  remove  extremely  minute  quantities  of  metal.  But 
the  chief  interest  centres  round  the  action  of  the  scrape  in  a  larger 
variety  of  tools,  represented  by  taps,  dies,  some  saws,  and  files. 
Abrasion,  so  called,  by  the  gritty  points  of  grindstones  and  emery 
wheels,  may  seem  a  small  matter,  yet  it  looms  large  in  present 
practice,  and  in  fact  we  must  consider  it  as  a  true  cutting  action. 
Shearing  is  an  operation  which  takes  place  when  a  shaving  or  a 
sheet  of  metal  is  severed  in  detail,  or  diagonally,  instead  of  by  a 
straightforward,  or  sudden  cut.  The  detrusive  action  of  a  punch 
may,  or  may  not  partake  of  a  shearing  character.  In  each  case  a 
tool  angle  may  be  present,  or  not. 

We  begin  to  see  how  complicated  the  queston  of  tool  angles 
may  become.  There  are  several  tools  to  which  it  is  difficult  to 
assign  an  exact  place,  tools  which  are  not  true  cutting  instruments. 


TOOL  ANGLES. 


19 


if  measured  by  angle,  but  which  nevertheless  do  operate  in  effect 
as  such.  In  the  attempt  also  to  impart  cutting  angles  to  some, 
other  evils  are  magnified.  Shearing  and  cutting  are  sometimes 
combined,  one  to  counteract  the  other,  or  both  to  operate  in 
unison,  and  help  each  other.  In  saws  we  have  examples  of 
cutting,  and  of  scraping  teeth,  the  first  for  ripping  soft  woods,  the 
second  for  ripping  hard  woods,  and  cross-cutting  both  kinds.  The 
teeth  of  files  are  scrapes.  The  teeth  of  taps,  and  dies,  and  of 
milling  cutters  are  generally  scrapes,  but  some  have  a  slight  rake 
which  brings  them  under  the  head  of  cutting  tools.  Some  drills 
are  scrapes,  others  are  true  cutting  tools,  with  shearing  action  in 
combination.  Mo-st  tools  for  wood-boring  cut,  but  not  all,  and  of 
those  which  cut,  many  suffer  by  reason  of  the  cutting  forces  being 
unbalanced.  These  and  cognate  problems  will  receive  illustration 
in  the  various  sections  of  this  work  devoted  to  particular  groups  of 
tools. 


SECTION  L 

THE  CHISEL  GROUP. 


CHAPTER  II. 

Chisels  and  Allied  Forms  for  Woodworkers. 

tiquity  of  Chisels — Primitive  Forms  of  Stone,  Bronze,  and  Iron — Single  and 
Double-bevelled  Chisels — Cutting  Action  —  Angle  and  Edge  —  The  Wedge 
Principle  —  Splitting  Action — Operation  by  Thrust  or  Pressure — and  Per¬ 
cussion — Importance  of  Rigidity — Angles  of  Grinding  and  Sharpening — 
Skill  required  for  Operation — Methods  of  Holding — and  of  Thrusting — 
Grain — Plane  Surfaces — Paring  and  other  Chisels  compared — The  Axes 
and  Adzes — Control  of — Draw-knife — Carvers’  Chisels — Lock  Chisels — 
Turning  Chisels — Sharpening  Chisels — Permanence  of  Edges.  The 
Gouges — Antiquity  of — Outside  and  Inside  Types — -Eirmer  and  Paring — 
Millwrights’  and  Coachmakers’ — Curves  of  Gouges — Value  of  Paring 
Gouge — Carvers’  Gouges  —  Their  Varieties  —  Method  of  Operation  — 
Turning  Gouges — How  to  Use. 

The  chisels  are  the  oldest  tools,  for  Paleolithic  men  used 
them  in  the  form  of  axes,  roughly  chipped  from  flint, 
while  the  severed  flakes  served  as  tips  for  javelins,  and 
lances,  and  for  the  first  rude  drills  used  by  man.  The  Neolithic 
men  improved  on  these  primitive  tools  by  the  practice  of  grinding 
and  polishing  their  celts  (Latin,  celtis,  a  chisel),  and  in  a  crude 

fashion  they  seem  to  have  differen¬ 
tiated  true  chisels  and  gouges  from 
the  axe-like  celts,  besides  which 
many  examples  of  hafting  occur. 
But  they  at  first  hafted  with  a  hole 
in  the  handle,  into  which  the  celt 
or  other  implement  was  secured, 
being  easier  than  drilling  a  hole  in  the  stone.  To  lessen  risk  of  the 
handle  splitting,  the  hole  was  made  a  considerable  distance  from 
the  end  (Fig.  6).  The  two  were  often  secured  with  vegetable  fibre. 


CHISELS  FOR  WOODWORKERS, 


21 


The  older  axes  were  of  stone,  and  driven  into  their  handles. 
The  modern  one  is  of  steel,  and  the  handle  is  driven  into  its  eye — 
a  most  important  difference.  Apparently  thousands  of  years 
passed  before  the  present  method  of  handling  occurred  to  the 
minds  of  tool-users. 

The  true  chisel,  handled  for  direct  thrusting  by  the  hand,  is 
late  in  point  of  time.  Apparently  such  tools  were  unknown  until 
long  after  men  cast  tools  in  bronze.  Then  we  find  the  true  chisel, 
and  the  gouge. 

The  axe,  therefore,  is  the  oldest  of  all  tools — older  than  the 
adze,  or  the  chisel,  or  the  drill — and,  except  in  the  material,  and 
the  manner  of  handling,  it  resembles  the  modern  one. 

While  flint  was  chiefly  used  in  the  Paleolithic  times,  the 
Neolithic  men  also  employed  beside  flint,  basalt,  greenstone,  ser¬ 
pentine,  porphyry,  micaceous  grit,  for  their  celts. 

Not  until  men  had  acquired  the  art  of  casting  in  metals  was 
any  further  advance  possible.  But  the  Bronze  Period  of  human 
culture  is  exceedingly  rich  in  chisels,  axes,  and  allied  forms,  which 
bear  unmistakable  resemblances  to  those  of  the  present  time. 
Palstaves,  tanged,  and  socketed  chisels,  and  gouges  are  abundant, 
and  many  of  the  moulds  in  which  they  were  cast  have  also  sur¬ 
vived.  A  few  similar  forms  in  iron  of  a  later  date  have  escaped 
the  ravages  of  rust.  In  the  ancient  Swiss  lake  dwellings  iron 
axes,  with  holes  for  the  wooden  hafts,  have  been  found. 

The  bench  chisel — ^type  of  others — differs  from  the  chisel 
used  for  turning,  or  the  axe,  in  the  fact  that  the  wedge  formation 
given  to  it  is  imparted  by  bevelling  one  face  only.  In  this  respect 
it  resembles  the  adze.  This  distinguishes  it  from  those  tools  in 
method  of  operation,  inasmuch  as  the  chisel  will  pare  a  fairly  true 
surface  by  the  control  of  the  hand  in  conjunction  with  the  flat 
face  of  the  tool.  But  this  also  involves  the  necessity  of  keeping 
the  cutting  face  perfectly  level. 

The  chisel  having  a  single  bevel  only  is  late  in  point  of  time. 
It  marked  a  great  advance,  because  the  unbevelled  face  became 
a  guide  to  accurate  work,  differing  from  a  doubly  bevelled  tool, 
such  as  a  celt,  or  a  cold-chisel  type,  of  which  numerous  examples 
in  bronze  remain.  A  good  deal  of  correction  in  the  way  of  re¬ 
moving  fine  chips  and  scraping  must  have  been  necessary  with 
such  tools. 

The  difficulty  of  cutting  effectively  with  the  ancient  chisel  of 


22 


TOOLS. 


stone,  and  even  of  bronze,  seems  to  indicate  that  these  tools  were 
seldom  if  ever  used  otherwise  than  percussively,  of  which  the  axe 
and  the  hatchet  are  the  modern  representatives.  In  the  case  of 
the  smaller  chisels  there  is  evidence  of  the  use  of  the  mallet  in 
the  burred-over  heads.  So  that  really  three  of  the  most  important 
tools  of  the  chisel  type  are  operated  by  our  carpenters  to-day 
much  as  they  were  actuated  many  thousands  of  years  ago. 

Chisels  are  used  in  all  the  woodworking,  and  in  many  other 
trades  besides,  yet  each  trade  has  some  forms  peculiarly  its  own. 
Among  these  are  included  carpenters,  joiners,  pattern-makers, 
millwrights,  coach  and  waggon  builders,  turners,  coopers,  masons, 
slaters,  bricklayers,  sculptors,  engravers,  butchers,  and  so  on. 
Most  of  these  chisels  are  furnished  with  handles,  and  the  handles 
differ  also  from  one  another  in  several  respects,  depending  on  the 
method  of  use  of  the  tools.  (See  Chap.  XVI.)  The  proportions 
of  blades  in  respect  of  width,  and  length,  and  cross  sections  also 
vary  widely. 

The  action  of  this  great  family  of  chisel  tools  is  that  of  cutting, 
the  condition  of  which  is  that  one  face  lies  parallel  or  nearly  so 
with  the  face  being  cut,  and  the  bevel  makes  an  angle  therewith, 
which  may  range  from  lo  to  30  degrees.  The  razor,  the  shoe¬ 
maker’s  knife,  and  the  table  knives  are  chisel-like  tools  with  the 
smallest  angle,  while  axes  have  the  largest  angle  among  the  true 
chisels. 

It  is  necessary  to  distinguish  between  angle,  and  edge.  A 
keen  angled  tool  will  not  cut  shavings  if  the  edge  is  dulled. 
Sharpen  the  edge  on  the  hone,  without  altering  the  angle,  and 
the  tool  cuts  shavings  sweetly.  If  the  tool  were  acting  as  a  wedge 
only,  splitting  by  percussive  blows,  the  state  of  the  edge  would 
have  no  influence,  but  the  angle  of  the  wedge  only. 

But  the  degree  of  keenness  of  edge  is  related  to  angle,  when 
materials  of  different  kinds  are  being  cut.  A  keen  edge  is  equally 
desirable  for  cutting  soft  pine,  hard  oak,  harder  lignum  vitte,  or 
hardest  iron  and  steel,  but  the  tool  angles  have  to  be  different  in 
each,  to  back  up  the  edge  properly  and  by  supporting  it  to  its 
work,  they  prevent  it  from  being  crumbled  or  broken  away.  A 
chisel  angle  suitable  for  cutting  wood,  will  cut  lead,  and  copper 
easily,  and  tin  with  some  difficulty.  Very  minute  cuUings  can 
even  be  taken  off  well-annealed  malleable  cast  iron.  But  ordinary 
irons  and  steels  cannot  be  touched  except  by  adopting  larger 


CHISELS  FOR  WOODWORKERS, 


23 


angles,  and  using  percussion,  as  in  the  cold  chisel,  or  by  making 
the  rotation  of  work  effect  much  of  the  necessary  pressure,  as  in 
hand  turning,  or  by  adopting  the  mechanical  help  of  the  slide  rest 
to  keep  the  tool  up  to  its  task.  The  mere  thrust  of  a  tool,  sufficient 
in  wood  cutting,  is  impotent  to  sever  hard  metals,  however  keen 
the  edge  may  be,  and  however  wide  the  tool  angle. 

The  wedgelike  action  of  a  chisel  is  comparable  with  that  of  an 
inclined  .plane,  in  which  the  labour  of  drawing  a  weight  up  the 
slant  face  is  less  than  that  of  lifting  it  perpendicularly ;  in  the  pro¬ 
portion  which  the  length  of  the  inclined  plane  bears  to  the  per¬ 
pendicular  height.  A  wedge  may  be  regarded  as  two  inclined 
planes  placed  back  to  back. 

Tools  of  the  chisel  type  embrace  a  very  great  number  of  forms, 
diverse  in  appearance,  and  in  mode  of  application,  yet  having  a 
common  affinity  to  the  wedge.  A  wedge  may  possess  the  splitting 
property  merely,  or  it  may  divide  by  cutting,  the  difference  depend¬ 
ing  partly  upon  its  degree  of  obtuseness,  partly  upon  the  manner 
in  which  it  is  presented  to  the  material,  partly  also  upon  the  nature 
of  the  material  operated  on.  Thus,  an  axe  if  driven  into  the  end 
of  a  piece  of  wood,  in  the  direction  of  the  grain  fibres,  will  not 
actually  cut,  but  will  divide  the  wood  by  splitting  alone.  But  if 
it  be  employed  at  the  face  of  the  wood,  where  the  layer  of  fibres 
is  so  thin  as  to  yield  readily,  the  purely  cutting  action  will  pre¬ 
dominate.  The  same  remarks  will  hold  good  of  a  chisel  used  in 
the  same  way.  But  if  the  wood  is  to  be  divided  in  a  direction 
transversely  to  the  fibres,  neither  axe  nor  chisel  will  operate  by 
splitting,  but  the  cutting  action  must  of  necessity  be  continuous 
throughout,  and  then  the  saw  is  used. 

The  chisel,  therefore,  used  as  a  splitting  tool  is  the  oldest  type, 
its  most  familiar  representative  being  the  axe,  which  is  a  wedge  pure 
and  simple,  no  cutting  action  occurring  after  the  first  entrance  of 
the  edge.  The  line  of  cleavage  then  lies  in  advance  of  the  edge, 
the  fibres  being  forced  asunder,  and  the  edge  does  not  cut  at  all. 
Such  action  is  widely  different  from  that  of  paring.  It  is  only  of 
value  in  splitting  up  fairly  straight-grained  stuff,  its  most  familiar 
example  being  chopping  wood,  and  rending  builders’  laths.  In 
crooked  grain  and  across  the  grain  it  is  of  no  value,  nor  for  any 
substance  but  wood.  Such  action  has  little  in  common  with  the 
bench  chisel,  the  edge  of  which  is  instrumental  in  removing  a 
shaving,  thick,  or  thin,  away  from  the  cut  surface.  The  chisels 


24 


TOOLS. 


actuated  by  a  direct  thrust,  and  those  in  which  the  force  expended 
takes  place  at  right  angles  with  the  axis  of  the  chisel,  correspond 
with  another  classification.  All  the  early  chisels  belonged  to  the 
latter,  being  furnished  with  handles  or  hafts,  as  our  axes  and  adzes 
are  to-day. 

As  all  the  chisels  are  used  in  one  of  two  ways,  being  either 
thrust  to  their  work  by  simple  pressure,  or  driven  by  percussive 
action,  this  distinction  is  embodied  in  the  proportions  of  these 
tools,  and  to  a  slight  degree  in  their  cutting  angles.  Percussively 
acting  chisels,  which  have  to  stand  the  mallet,  like  mortise 
chisels,  or  have  to  be  driven  by  the  swing  of  a  lever,  like  the  axe 
and  adze,  must  be  made  stouter  than  the  paring  tools  which  are 
simply  thrust,  or  they  would  become  fractured  by  the  severe  con¬ 
cussions  to  which  they  are  subject.  Their  cutting  angle  must  also 
be  slightly  more  obtuse,  or  the  edge  would  be  lost,  either  by 
simple  dulness,  or  by  the  breaking  out  of  fragments  of  metal, 
especially  in  tools  that  have  been  tempered  rather  highly.  This 
difference  is  not  so  apparent  in  the  simple  action  of  paring,  as  it  is 
when  the  tools  are  used  more  in  the  character  of  wedges,  deeply 
buried  in  the  wood,  and  acting  partly  by  cutting,  but  often 
more  largely  by  cleavage. 

The  exact  degree  of  cutting  angle  of  chisels  is  generally 
disguised  by  the  fact  that  the  sharpened  angle  is  greater 
than  the  ground  one.  But  a  wider  angle  is  usually  adopted 
for  percussive  work  than  for  simple  pressure,  and  for 
operating  on  hard,  tough,  stringy  woods  than  on  soft, 
open  grained  ones.  It  is  always  much  less  than  the  angle 
for  metal-cutting  chisels,  e.g.,  the  cold  chisel,  the  turner’s 
and  planer’s  roughing  tools,  knife  tools,  and  others  that 
remove  shavings  from  metal. 

Many  tools  of  the  chisel  family  are  operated  indif¬ 
ferently  by  pushing,  or  by  percussion ;  as  for  example  the 
firmer  chisels,  and  those  for  millwrights,  coachmakers,  and 
others.  But  in  the  extreme  types  there  is  but  one  method 
of  use  adopted.  I-ong,  thin,  paring  chisels  (Fig.  7)  are 
seldom  struck  by  a  mallet.  They  are  liable  to  fracture, 
and  even  if  they  do  not  break,  they  spring.  Neither  are 
draw-knives,  or  turning  chisels  ever  struck.  But  the  axe, 
and  the  adze  group  are  always  used  percussively,  and  so  are  many 
others. 


Fig-  7- 


CHISELS  FOR  WOODWORKERS.  25 

The  efificiency  of  any  chisel  depends  to  a  considerable  extent 
on  its  rigidity.  This  is  apparent  when  attempting  to  cut  thick 
chips  with  a  slender  paring  chisel.  It  springs,  and  would  chatter, 
and  jump  away  from  its  work  if  forced  hard.  In  an  extreme  case, 
try  to  slog  out  a  mortise  with  a  paring  chisel.  To  cut  mortises 
properly,  an  extra  stout  chisel  is  made  for  the  purpose  (Fig.  8),  which 
will  neither  spring,  nor  snap  under  the  heaviest 
work.  It  is  very  thick — nearly  square  in  cross 
section — while  the  paring  tool  is  very  thin,  and 
often  also  has  its  top  edges  bevelled,  as  in  Fig.  7. 

Then  the  handle  in  the  latter  is  comparatively 
slender,  while  that  of  the  former  is  massive. 

That  of  the  paring  tool  is  bellied,  to  be  grasped 
easily  in  the  hand ;  that  of  the  mortise  is  of  no 
particular  shape,  since  it  is  simply  steadied  and 
controlled  by  one  hand,  while  the  blows  of  the 
mallet  are  delivered  by  the  other.  If  paring 
chisels  are  struck  by  the  mallet,  as  they  are 
sometimes,  the  blow's  must  not  be  severe,  or  the 
jar  is  liable  to  snap  them.  To  pare  with  a 
mortise  chisel,  on  the  other  hand,  is  almost 
impossible.  Midway  between  the  extreme  types 
are  the  firmer  or  short  chisels,  and  the  coachmakers’  chisels  (Fig. 
9),  which  have  to  stand  some  hard  duty  imposed  by  the  con¬ 
cussion  of  the  mallet ;  and  the  turning  tools,  which  are  fitted  to 
withstand  occasional  concussion,  besides  the  steady  strain  of  deep 
cutting. 

The  bevelled  face  includes  the  ground  bevel,  and  the 
sharpening  bevel,  the  first  of  which  remains  constant,  the 
second  always  tends  to  increase  the  cutting  angle,  due  to  re¬ 
sharpening.  On  first  sharpening  a  newly  ground  chisel,  there  will 
be  little  difference  in  the  angle  of  the  grinding  and  sharpening, 
and  at  that  period  the  tool  cuts  most  sweetly.  When  by  re¬ 
sharpening  the  angle  becomes  thickened  to  such  an  extent  that 
cutting  is  not  sufficiently  free,  or  re-sharpening  takes  a  long  time ; 
then  it  is  more  economical  to  re-grind. 

The  angles  at  which  chisels  and  gauges  are  sharpened  should 
vary  a  little  with  the  work  on  which  they  are  used,  and  also  slightly 
with  the  known  temper  of  the  tools.  Tools  are  sometimes  so  hard 
and  brittle  that  it  is  impossible  to  grind  them  thin  ;  for  contact 


pi 


O 

Fig.  8.  Fig.  9. 


26 


TOOLS. 


with  a  knot,  or  a  slight  amount  of  malleting  suffices  to  break 
pieces  out  of  the  keen  cutting  edges.  But  if  ground  more 
obtusely  they  form  splendid  tools,  cutting  sweetly,  and  keeping 
their  edges  good.  Other  conditions  being  equal,  tools  used  on 
soft  wood  will  bear ,  more  acute  grinding  than  for  hard  woods. 
This  is  no  more  than  we  should  expect ;  but  the  error  consists  in 
supposing  that  a  tool  sharp€?ied  “  thick  ”  must  needs  cut  well  on 
hard  wood.  It  will  not,  since  the  edge  has  little  penetrative  power. 
We  must  not  ignore  the  wedgelike  action  of  the  tool.  A  chisel 
will  also  cut  more  sweetly,  if  instead  of  being  forced  directly  down¬ 
wards,  or  across,  the  wood  as  the  case  may  be,  it  is  moved  in  a 
slightly  oblique  direction.  This  combines  the  wedgelike,  with 
the  shearing  action,  and  produces  a  clean  cut  face,  even  though 
the  edge  happens  to  be  a  little  dulled.  It  will  be  found  also  that 
less  muscular  effort  is  required. 

The  chisel  in  all  its  forms  requires  more  skill  in  its  manipula¬ 
tion  than  some  other  tools,  such  as  the  plane,  or  spoke-shave, 
because  the  degree  of  accuracy  of  its  operation  depends  on  the 
control  afforded  by  the  workman’s  hands ;  it  is  also  less  easy  to 
control  the  percussive  chisels,  as  the  axe  and  the  adze,  than  the 
paring  tools.  In  paring,  the  tool  is  set  or  placed  against  the  face, 

or  the  line  to  be  cut  by,  as  in  Fig.  lo. 
In  the  axe  and  adze  the  eye  determines 
the  location  of  the  blow  delivered  by  the 
hand — a  task  requiring  skill  born  of  prac¬ 
tice.  A  man  unaccustomed  to  the  adze  can 
do  nothing  accurate  with  it ;  one  skilled  in 
its  use  will  control  its  action  within  a  sixteenth  of  an  inch.  The 
training  of  the  hand  and  eye  is  a  mutual  one.  The  direction  and 
extent  of  a  percussive  cut  cannot  be  altered  after  it  is  once 
started ;  that  of  a  paring  tool  can.  Thus  the  latter  is  capable  of 
producing  the  more  accurate  results.  In  order  to  produce  the 
best  work  with  the  axe,  using  it  as  a  trimming  tool,  rather  than  as 
one  for  splitting,  the  single-grinding  bevel  should  not  be  departed 
from  in  sharpening.  If  the  bevel  for  sharpening  is  different  from 
that  of  grinding,  the  power  of  control  is  lessened.  The  advantage 
which  the  adze  possesses  over  the  axe  for  correct  work  is  due  to 
the  fact  that  all  the  bevel  is  on  one  face ;  the  face  in  contact  with 
the  work  being  cut  is  not  ground  at  all.  It  would  be  flat,  but  for 
the  necessity  of  imparting  a  convexity  to  that  face  (Fig.  15,  p.  30), 


Fig.  10. 


CHISELS  FOR  WOODWORKERS. 


27 


about  equal  to  the  radius  through  which  the  adze  is  swung.  The 
difference  between  these  tools  and  the  chisel  having  one  face  quite 
flat  is  apparent,  and  the  nearer  they 
resemble  the  chisel  the  more  accurate 
will  the  results  be  which  they  produce. 

The  way  in  which  a  chisel  should 
be  held  when  in  use  depends  on  the 
position  of  the  work.  Most  cutting  is 
done  with  the  tool  held  perpendicu¬ 
larly,  the  work  lying  on  the  bench. 

When  paring  vertically,  the  wrong  way 
to  hold  the  chisel  is  to  elevate  the 
elbow,  and  grip  the  handle  at  the  end 
and  press  downwards  with  the  palm 
of  the  hand.  That  is  the  method  of 
the  beginner.  The  right  way  is  to 
clasp  the  body  of  the  handle  in  the 
closed  hand,  with  the  elbow  slightly 
depressed,  and  to  exercise  pressure 
downwards  in  the  direction  of  the  axis 
(Fig.  ii). 

The  chisel  edge  generally  has  to  be  set  into  lines  scribed,  or 
otherwise  marked  on  the  surface  of  the  work.  So  that  while  the 
right  hand  is  thrusting  the  chisel,  the  left  is  controlling  its  cutting 
edge  by  resting  partly  on  the  work  and  partly  against  the  chisel. 
Of  course,  after  the  lines  have  been  set  in,  the  cut  surfaces  afford 
sufficient  controlling  influence.  A  fair  amount  of  work  is  also  held 
in  the  vice,  and  the  chisel  held  horizontally.  To  cut  thus,  the 
wrong  way  is  to  grasp  the  body  of  the  handle ;  the  right  is  to  grip 


Fig.  12. 


it  at  the  end,  and  to  thrust  it  forward  with  the  palm  of  the  right 
hand,  steadying  it,  if  need  be,  with  the  left  (Fig.  12).  To  pare 


28 


TOOLS. 


small  work  held  in  the  left  hand,  the  chisel  is  grasped  by  the  body 
of  the  handle  (Fig.  i.^). 

The  direction  of  thrusting 
a  chisel  has  much  influence 
on  the  results.  When  cut¬ 
ting  vertically  above  the 
bench  as  in  Fig.  ii,  the 
effort  is  little  more  than  that 
of  the  muscles  of  the  arm. 
But  when  cutting  horizontally 
by  thrusting  (Fig.  12),  much 
of  the  weight  of  the  body 
can  be  thrown  into  the  work. 
One  hand  only  can  be  con¬ 
veniently  used  in  a  vertical  cut,  but  two  may  be  frequently 
employed  when  shaving  horizontally. 

The  chisel  is  ill  adapted  for  cutting  along  the  grain  with  any 
great  precision,  though  suitable  for  roughing-down  in  that  direc¬ 
tion.  If  the  grain  is  not  very  straight,  the  tool  will  follow  it,  and 
tear  up  the  surface  in  those  places  where  the  fibre  runs  downwards 
or  away  from  the  cutting  edge.  Then  the  work  must  be  reversed, 
and  when  that  is  not  practicable,  very  thin  and  light  cuttings  only 
must  be  removed.  A  chisel  working  across  the  grain  avoids  these 
evils,  but  the  surface  left  is  not  smooth — a  shearing  cut  being 
required.  The  cutting  of  end  grain  is  most  satisfactory,  since  that 
can  be  left  very  clean  and  smooth  and  true,  provided  the  chisel 
is  quite  sharp. 

The  force  required  to  operate  a  chisel  varies  with  its  width, 
and  with  the  thickness  of  the  chip,  and  therefore  there  comes  a 
limit  to  its  effective  operation  by  hand.  A  width  of  i-|-  in.  is 
about  as  much  as  one  can  use  in  cutting  chips  of  moderate  thick¬ 
ness,  combined  with  the  production  of  a  reasonably  true  face.  To 
sever  thick  chips  of  such  a  width  is  hard  work.  To  remove  those 
of,  say,  ^  in.  thick,  even  with  a  narrow  mortise  chisel,  is  beyond  the 
power  of  the  hand  alone,  and  so  here  the  mallet  is  brought  in. 

No  chisel  possesses  such  perfect  guidance  as  the  planes  do, 
and  yet  by  practice,  surfaces  of  three  or  four  inches  in  width  are 
constantly  being  finished  by  the  chisel  alone.  Here  the  value  of 
the  paring  tools  over  the  firniers  is  apparent.  A  firmer  chisel  is  a 
stumpy  article  to  use  for  broad  cuts.  One  has  to  work  in  a  more 


CHISELS  FOE  WOODWORKERS 


29 


cramped  posture  with  it  than  with  a  paring  chisel.  The  latter, 
moreover,  can  be  kept  flat  on  the  surface  being  cut  for  a  length  of 
several  inches,  provided  the  chisel  has  a  nice  straight  face.  It 
should  never  be  tipped  up  on  that  face  when  sharpening. 
Frequently  an  end  can  be  finished  more  neatly  by  holding  the 
work  in  one  hand,  and  taking  very  light  cuts,  as  in  Fig.  13, 
turning  the  wood  about,  and  cutting  first  in  one  direction,  and 
then  in  the  other. 

Since  a  paring  chisel  is  so  slender  that  it  springs  in  the  longi¬ 
tudinal  direction  when  the  attempt  is  made  to  cut  deeply  with 
it,  especially  on  end  grain,  here  therefore  the  millwright’s  or 


coachmaker’s  chisel  (Fig.  9)  fills  a  valuable  place.  This  is  used 
both  as  a  paring  chisel  in  heavy  cutting  on  hard  woods,  or  for 
medium  heavy  malleting.  In  this  respect  it  occupies  a  place 
between  the  firmers,  the  mortise  chisels,  and  the  paring  tools. 

The  chisels  which  are  regularly  driven  by  the  mallet  are  much 
stiffer  than  the  millwright’s  and  coachmaker’s.  They  include 
principally  the  tanged  mortise,  and  the  socket  mortise  chisels 
(Fig.  8),  made  in  their  several  varieties  to  suit  different  trades. 
Though  differing  in  length,  all  alike  are  characterised  by  a 
thickness  approximately  twice  or  three  times  as  great  as  that  of 
the  firmer,  and  paring  tools.  They  have  a  very  marked_amount  of 


3° 


TOOLS. 


taper,  so  that  they  can  be  malleted,  and  also  used  as  levers  to 
push  the  chips  back  from  the  cut  face,  and  to  dig  them  out  of 

their  holes.  Proportions  vary,  thus  : — 

A  cabinetmaker’s  chisel  is  rather 
lighter  than  the  carpenter’s.  A  sash 
chisel  is  made  more  slender  than  the 
carpenter’s.  The  chairmaker’s  tool  is 
shorter,  and  more  stumpy  than  either. 
A  mortise  chisel  used  for  locks  is  bent 
similarly  to  the  carver’s  in  order  to  permit 
of  scooping  out  the  chips  (Fig.  14).  In 
the  socket  types,  variations  occur  in 
length,  and  in  substance.  These  will 


stand  more  punishment  than  the  tanged 
chisels,  the  sockets  lessening  risk  of 
splitting  the  handles  by  hard  malleting,  and  in  that  their  chief 
value  lies.  Except  for  cutting,  and  clearing  away  at  the  finish, 
these  tools  are  invariably  driven  with  the  mallet. 


Fig.  16. 


Fig.  17. 


Many  chisels  have  their  back  or  upper  edges  bevelled  (Fig.  7), 
to  permit  of  cutting  along  within  the  edges  of  acute  angles,  as 
those  of  dovetails.  An  alternative  to  this  form  is  a  convex  back, 
less  used  however  than  the  bevelled. 


[ 

Fig.  18.  Fig.  19. 

That  large  group  of  the  chisel  family  which,  though  percussive, 
is  not  actuated  by  a  mallet,  but  by  the  swing  of  a  lever,  includes 
the  adze  (Fig.  15)  and  the  axe  (Figs.  16  and  17),  the  various 
choppers  (Fig.  18),  and  cleavers,  the  bill  hook  (Fig.  19),  the 


CHISELS  FOR  WOODWORKERS 


31 


Fig.  20. 


chisel-pane  hammers  (Fig.  20),  boiler  scaling  hammers,  and  allied 
forms.  The  width  of  blade  in  most  of  these  considerably  exceeds 
that  of  the  chisels.  There  is  no  guidance  at  all  for 
starting  an  operation,  but  cutting  to  a  line  is  a  work  of 
skill  on  the  part  of  the  craftsman.  And  yet  in  the  case 
of  the  axe  and  adze,  very  close  results  can  be  obtained. 

Cleavers,  choppers,  bill  hooks,  and  the  lath-hammer,  or 
lath-render  (Fig.  21),  are  employed  as  instruments  for 
severance  only,  or  chiefly,  but  the  adze  and  axe  are  in 
a  sense  finishing  as  well  as  roughing  tools.  Within 
their  sphere  they  are  unapproachable  by  any  tool  whatever,  that 
sphere  being  the  shaping  of  rough  balks  and  branches  of  timber 
into  straight  and  curved  outlines  for  various  purposes. 

Adzes  are  used  by  shipwrights,  carpenters, 
coopers,  wheelers,  platelayers.  They  differ 
in  length  of  blade,  in  curvature,  and  in  the 
formation  of  the  head,  which  is  generally 
finished  to  serve  as  a  hammer. 

Axes  or  hatchets  are  made  in  many 
forms,  each  with  its  distinguishing  name  in  the  trade.  The  most 
marked  difference  occurs  perhaps  in  the  English,  and  Yankee 
pattern  (Figs.  16  and  17  respectively). 

The  efficiency  of  adze  and  axe  depend  to  a  large  extent  on  the 
long  swing  of  the  handles,  by  which  they  are  distinguished  from 
most  of  the  other  chisel-like  tools.  In  those  which  resemble  them 
most  nearly,  the  butcher’s  cleavers,  meat  choppers,  and  bill  hooks, 
the  handles  are  much  shorter;  but  the  latter  score  in  greater 
length  and  weight  of  blade. 

'I'he  utilities  of  the  chisel  family  are  not  confined  to  the 
obvious  one  of  removing  shavings  or  splitting.  A  bricklayer’s  axe 
for  example  is  a  broad  knife  by  means 
of  which  a  nick  is  produced  around 
the  brick,  after  which  a  blow  of  the 
hammer  severs  it.  The  slater’s  saxe 
(Fig.  22)  acts  in  a  similar  fashion  by 
nicking,  and  other  examples  occur  to 
the  mind. 

The  pick  in  its  various  forms  is  a  chisel  in  which  the  point 
takes  the  place  of  an  edge.  It  does  not  sever,  but  splits.  It  is  a 
cleaving,  not  a  shaving  tool.  The  coal  pick,  and  the  navvy’s  pick 


32 


TOOLS. 


are  tools  in  common.  Somewhat  similar  is  the  marline  spike  used 
for  forcing  the  strands  of  rope  apart  when  splicing. 

A  miner’s,  or  rock  drill  (Fig.  23),  is  a  percussive  tool ; — in 
effect  two  chisel  points  at  right  angles,  which  is  turned  upon  its 


■4 


Fig.  23. 


Fig.  24. 


axis,  and  thrust  to  the  rock  which  it  breaks  up.  A  quarry  jumper 
is  a  single  chisel  edge  (Fig.  24),  operated  similarly. 

Only  in  a  slight  degree  do  any  of  these  tools  possess  guidance  in 
themselves,  even  after  a  cut  or  a  split  is  started,  for  they  have  no 
flat  faces  like  the  firmer,  and  paring  chisels  possess,  but  are  either 
doubly  bevelled  as  in  the  axes,  or  the  cutting  face  has  considerable 
curvature  as  in  the  adzes  (Fig.  15).  After  the  cutting  of  a  face 
has  commenced,  the  portions  first  cut  help  to  control  the  move¬ 
ments  of  these  tools,  which  are  arrested  by  the  cut  faces.  The 
surfaces  left  are  short  facets,  each  one  formed  independently  of  the 


more  of  the  wedge,  and  less 
than  of  shaving.  In  using 


others,  differing  in  this  aspect 
from  the  face  left  by  a  chisel, 
which  lies  flat  upon  its  work. 
The  degree  of  control  exer¬ 
cised  upon  the  axe  and  adze 
makes  all  the  difference  be¬ 
tween  good  and  poor  results, 
and  this  has  to  be  acquired ; 
the  tool  formation  rendering 
no  aid  as  it  does  in  the  chisel, 
or  in  a  more  complete  manner 
in  the  planes.  Both  axe  and 
adze  tend  either  to  “  strike 
off”  from  the  work,  or  to 
stick  fast  in  it.  The  first 
happens  when  fine  cutting  is 
attempted,  the  second  when 
slogging  is  being  done.  Cut¬ 
ting  of  the  latter  class  partakes 
the  chisel  action,  of  splitting  more 
hatchet,  a  little  support  can  be 


CHISELS  FOR  WOODWORKERS. 


33 


Fig.  26. 


derived  by  keeping  the  right  arm  close  to  the  body,  but  in  using 
an  adze,  support  is  obtained  by  resting  the  elbows  and  arms  close 
against  the  ribs.  After  considerable 
practice  a  man  may  become  more  ex¬ 
pert  with  the  adze,  than  with  the  axe. 

A  chisel  is  often  used  as  a 
roughing  tool  on  the  bench  in  place 
of  the  axe.  Pieces  of  wood  that  have 
to  be  turned  down  between  centres 
have  their  keen  angles  cut  off  with  a 
chisel,  as  being  more  rapid  in  action 
than  the  plane,  with  the  stuff  laid  in 

an  angle  board.  Chips  are  cut  off  with  the  chisel  face  next  the 
piece,  the  work  being  pressed  against  the  bench  stop.  Or  often 
the  back  of  the  chisel  is  employed  to  rough  down  an  edge 
preparatory  to  planing,  the  stuff  being  held  vertically  (Fig.  25), 
the  mode  of  cutting  then  resembling  that  of  the  axe. 

The  draw-knife  (Fig.  26)  owes  much  of  its  value  to  its  two 
handles,  which  enable  both  hands  to  be  utilised,  so  that  very 
thick  chips  can  be  cut  off  the  edges  of  boards  held  in  the  vice, 
being  almost  as  stout  as  those  which  an  axe  would  cut.  And  the 
draw-knife  is  simply  a  very  broad  chisel  fitted  with  two  handles, 
by  which  the  tool  is  pulled  or  drawn  towards  the  workman. 

Draw-knives  occur  in  several  patterns,  and 
sizes,  straight  and  curved  in  the  blade,  and  with 
handles  parallel,  or  divergent.  Carpenters,  joiners, 
mastmakers,  wheelers,  and  coopers  use  them. 

The  intricacies  of  wood  carvers’  work  are 
reflected  in  a  number  of  tools,  all  of  small  size, 
but  greatly  varied  in  outline.  There  are  straight 
chisels,  square  across  the  cutting  edge,  and  skew, 
or  on  a  bevel.  There  are  also  spade  chisels, 
both  square,  and  skew.  The  vee  tools,  or 
parting  tools  (Fig.  27),  are  in  effect  two  chisels 
set  at  various  angles,  acute,  and  obtuse,  for 
cutting  angular  grooves  of  corresponding  shapes, 
and  these  are  both  straight  and  curved  longi¬ 
tudinally.  The  dog-leg  chisel  comprises  a  narrow  chisel  formed 
at  the  end  of  a  long  cranked  shank. 

The  turning  chisel  (Fig.  28)  is  an  example  of  a  mixed  character. 

c 


Fig.  28. 


34 


TOOLS. 


Its  guidance  does  not  depend  on  the  sharpened  faces,  since  it  has 
a  double  bevel  in  the  style  of  the  axe.  Yet  it  is  not  a  percussive 
tool,  and  it  is  not  thrust  with  much  force  to  its  work.  It  is  held, 
controlled,  and  guided  by  the  hands,  in  combination  with  the 
support  afforded  by  the  rest  (Fig.  29).  It  does  not  cut  over  its 
entire  width,  but  only  over  one-third  or  one-fourth  of  the  same. 
Its  action  is  so  keen  that  it  will  cut  with  or  across  the  grain,  or  on 


end  grain  with  almost  equal 
facility. 


The  gouges  are  true 
chisels,  curved  in  cross 
section.  The  remarks  that 
have  been  made  about  the 
difference  between  firmer 
and  paring  tools,  of  chisels 


yjg  29.  Fig.  30.  operated  by  thrust  and  by 

percussion,  apply  to  gouges. 
The  latter,  however,  do  not  occur  in  so  large  a  range  of  sub-types, 
neither  are  the  adze  and  axe-like  tools  represented  among  the 
gouges. 

Gouges  of  bronze  occurred  in  great  numbers  in  the  Neolithic 
Age,  some  being  of  the  tanged,  others  of  socketed  types  (Fig.  30). 
The  idea  of  curving  the  chisel  to  enable  it  to  form  concave  pro¬ 
files  is  therefore  some  two  or  three  thousand  years  old. 

There  are  two  great  groups  of  gouges,  the  outside  and  the 
inside,  the  terms  denoting  the  method  of  grinding;  the  outside 
gouge  having  its  bevel  for  grinding  and  sharpening  on  the  convex 
or  outer  face,  the  inside  gouge  being  ground  on  the  inner  or 
concave  face.  The  former  group  are  also  firmer  or  short  gouges, 
the  latter  are  paring  or  long  gouges,  the  relative  lengths  of  which 
have  their  analogies  in  the  firmer  and  paring  chisels.  The  paring 
gouges  were  developed  by  the  necessities  of  the  millwrights  and 
patternmakers,  and  they  are,  like  the  chisels,  made  stout  and 
heavy,  and  thin  and  light. 

The  firmer  and  paring  gouges  are  used  like  the  chisels  of 
the  same  name,  the  firmer  chiefly  with  the  mallet,  and  the  latter 
by  hand  thrust  or  pressure  almost  wholly.  Exceptions  occur  in 
the  millwright’s  or  coachmaker’s  paring  gouges,  which  are  made 
stiff  enough  to  endure  malleting,  and  in  a  small  group  of  firmer 
gouges,  which  is  ground  inside  instead  of,  as  usual,  on  the  outside. 


CHISELS  FOR  WOODWORKERS. 


35 


The  curves  of  the  paring  and  firmer  gouges  are  divided 
between  groups,  so  that  a  gouge  of  any  one  width  can  be  obtained 
in  either  one '  of  six  different  curvatures. 

Formerly  there  were  three  available,  quick, 

flat,  and  middle  ffat,  but  now  a  range  of  six 

is  obtainable,  designated  as  A,  B,  C,  D,  E,  F 

groups.  Two  of  these,  the  extremes,  are 

shown  in  Figs.  31  and  32  for  gouges  up  to  i  ^  ^ 

inch  in  width.  Gouges  are  made  from  ^  to  2 

inches  wide,  but  the  generally  useful  sizes  are 

included  between  and  i|  inch. 

The  paring  gouge  is  very  valuable  not  only  - - 

as  a  finishing  tool  but  as  a  roughing-out  tool. 

There  is  k  great  deal  of  work  which  cannot  be  - 

put  under  the  band  saw,  and  for  this  a  broad 

quick  gouge  is  the  best  possible  slogger. - 

What  are  termed  the  “  trowel  shank  ”  or 

“  spoon  gouges  ”  are  excellent  forms  for  this,  ^  _ 

because  the  knuckles  do  not  come  in  contact  yjg.  ^i. 

with  the  work.  As  in  chisels,  the  working  face 

of  a  paring  gouge  must  be  true,  if  true  cutting  is  to  be  done. 

A  great  group  of  gouges  is  that  used  by  carvers.  They  include 
straight  gouges  in  numerous  sweeps,  and  gouges  curved  in  the 
longitudinal  direction,  capable  therefore  of  cutting  concave  shapes 
in  two  directions ; — that  corresponding  with  the  curve  of  gouge 

section,  and  the  other  variable,  but  to 
k  some  extent  controlled  by  the  longi- 
I  tudinal  curve  of  the  gouge. 

'  The  carver’s  gouges  may  be  ranked 
as  firmer  gouges,  being  all  short,  but 
they  form  a  class  alone,  since,  though 
some  are  straight  lengthwise,  the  great 
majority  of  them  are  curved  or  “  bent  ” 
in  that  direction,  the  object  of  which  is 
to  permit  of  their  cutting  into  curves 
)  of  very  small  radius,  in  the  longitudinal 
direction  of  movement  of  the  gouge. 
They  are  “front  bent,”  and  they  are 
“bent  back”;  made  also  with  long  curves,  and  with  short  quick 
ones,  or  “  spoon  bit  ”  (Fig.  33)  and  “  spade  ”  type,  and  each  in  a 


36 


TOOLS. 


Fig-  34- 


wide  range  of  sizes,  from  extremely  flat  forms  to  “  quick,”  up  to 
half  circles.  The  widest  of  these  tools  do  not  exceed  about  |  in. 

in  breadth.  Extreme  sectional  curves  are  shown  in 
Fig.  34- 

Patternmakers  use  some  of  the  carver’s  tools, 
chiefly  the  curved,  and  front  bent  gouges,  for  cutting 
the  interiors  of  core  boxes,  especially  for  the  “  hollow  ” 
portions,  or  radii  of  recessed,  or  chambered,  or 
shouldered  parts  of  boxes. 

The  carver’s  tools  are  driven  by  the  mallet  in 
roughing  out,  but  in  finer  cutting  they  are  more  often 
thrust  by  the  ball  of  the  right  hand,  concussively,  and  in  finishing 
cuts  they  are  simply  held  in,  and  thrust  by  the  hand. 

The  turning  gouge  is  shown  in  Fig.  35.  In  the  hands 
of  a  professional  wood-turner  a  simple  gouge  is  a  marvellous 
tool,  producing  hollows,  ogees,  and  mouldings  of  various 
shapes  with  swift  dexterity,  aided  only  by  the  chisel  where 
sharp  corners  are  concerned.  Those  who  handle  the 
gouge  with  confidence  and  skill  can  turn  out  their  work 
quicker,  cleaner,  and  better  than  those,  who,  dreading  a 
disastrous  “kick,”  or  “catch,”  scrape  away  cautiously  with 
the  round  nose,  and  chisel,  and  diamond  point.  An  inch 
gouge,  that  is  i  in.  wide,  is  the  largest  that  can  be  well 
used  with  a  light  treadle  lathe,  and  to  use  that  effectively 
means  hard  leg  work.  A  ^  in.,  |  in.,  or  ^  in.  will  be  more 
generally  useful  by  far.  The  gouges  should  be  well  Fig.  35. 
rounded  in  grinding  (Fig.  36),  so  that  the  point,  and 
not  the  corners  shall  be  used  for  cutting,  and  they,  in  common 
with  most  of  the  other  tools,  should  be  furnished 
with  long  handles,  to  afford  adequate  leverage  and 
control. 

In  turning  straight  along,  either  between  centres, 
or  on  the  face  plate,  the  gouge  may  be  held  flat  on 
its  back  without  any  danger  of  its  catching  in  the 
wood ;  but,  in  turning  mouldings,  and  in  boring 
holes  with  the  cup  chuck,  the  tool  must  be  held 
sideways,  and  the  corner  of  the  gouge  which  is 
lowest,  or  rather  some  portion  of  that  half  the  gouge 
which  is  lowest,  is  the  one  which  will  be  used  for  cutting, 
the  higher  corner  being  kept  carefully  away  from  the  revolving 


Fig.  36. 


CHISELS  FOR  WOODWORKERS. 


37 


wood  to  prevent  a  catch.  Even,  however,  in  rapidly  roughing 
down  plain  straight  surfaces,  it  is  advantageous  to  handle  the 
gouge  in  this  fashion,  using  both  sides  alternately,  since  it  cuts 
the  wood  cleaner,  quicker,  and  with  less  friction  than  when  used 
on  the  flat.  This  is  a  lesson  only  to  be  learned  by  practice. 
The  great  thing  is  to  feel  the  work.  Thus,  if  turning  down  a 
moulding,  or  a  ball  at  the  end  of  a  curtain  pole,  from  circum¬ 
ference  towards  the  centre,  there  is  the  centrifugal  force  very 
sensibly  tending  to  thrust  the  gouge  outwards,  and  this,  of  course, 
is  the  force  wTich  must  be  resisted.  The  point  of  the  gouge,  or  a 
portion  just  below  the  point,  will  be  used,  as  offering  least  friction, 
and  the  tool  must  be  grasped  very  firmly.  In  turning  a  flat 
surface,  no  such  force  exists,  and  the  gouge  may  be  held  indiffer¬ 
ently  in  any  position,  and  comparatively  slack.  Always  the  end 
of  the  gouge  handle  is  held  in  the  right  hand,  while  the  three  last 
fingers  of  the  left  grasp  the  lower  portion  of  the  gouge  itself. 
The  requisite  guidance  is  imparted  to  the  tool  by  the  thumb  of 
the  left  hand,  while  the  opposite  forefinger  passes  underneath  the 
rest,  in  opposition  to  the  thumb,  thus  gripping  the  tool  as  in  a 
vice.  Lastly  the  rest  must  be  kept  close  up  to  the  work. 


CHAPTER  III. 


Planes. 

Great  Variety  in — Setting  of  Chisel  or  Iron  in  its  Stock — Fastening  of 
the  Iron — Convexity  of  Same — Choking — Utility  of  Top  Iron — The 
Question  of  Angles,  as  affected  by  Re-sharpening — Linear  Guidance — 
Related  to  Length  of  Stock — Preservation  of  Truth  of  Face — Planes  for 
Concave  Sweeps — The  Profiles  of  Planes — Drawbacks  to  the  Moulding 
Planes — Iron  Planes — Gripping  of  Planes — Pressure  on— -Guidance  of — 
Aids  derived  from  Shooting,  and  Angle  Boards — The  Aid  of  Strips — 
Checking  the  Truth  of  Planed  Surfaces — Details  of  Planing — Faces — 
Ends — Setting  Irons  in  Slocks — Removal  of  Irons — Good  and  Bad 
Timber — Sharpening  Moulding  Planes — Wear  and  Tear  of  Planes — 
Shooting — Mouthpieces — Selection — and  Preservation  of  Planes — Tooth¬ 
ing  Planes. 

A  CHISEL,  to  possess  linear  guidance,  must  have  its  flat 
face  coincident  with  the  surface  being  cut.  Thus,  it 
would  be  impossible  to  cut  the  surface  a.  Fig.  37,  truly 
with  the  chisel  held  at  an  angle,  as  there  shown.  But  if  it  is 
inserted  at  an  angle  in  a  stock,  it  becomes  a  plane,  which  pro¬ 
duces  true  surfaces  beyond  the  capacity 
of  a  mere  chisel  to  operate  upon. 

The  mechanic  who  first  put  a  chisel  in 
a  wooden  stock  to  supplement  the  un- 
Fig-  37-  certain  control  of  the  hand  led  the  way 

to  an  infinite  line  of  inventions,  of  a 
similar  character.  This  device  involved  the  distinction  between 
the  chip  and  the  shaving,  between  the  uncertain  and  the  precise, 
the  slow  and  the  expeditious,  and  finally  in  its  later  developments, 
between  the  puny  weakness  of  the  human  arm  and  the  practically 
unlimited  giant  power  of  machinery.  Specifically  we  confine  our 
attention  here  to  the  common  planes,  leaving  alone  the  vast 
number  of  applications  of  the  principle  of  guidance  that  are 
embodied  in  the  tools  which  are  controlled  in  machines. 

The  different  kinds  of  planes  now  made  number  hundreds. 


PLANES. 


39 


Almost  any  form  of  cutter  can  be  put  in  a  stock,  while  the  shape 
of  the  latter  can  be  so  modified  as  to  suit  work  corresponding  with 
the  sectional  shapes  of  the  cutting  irons,  as  in  the  moulding  planes, 
and  the  proportions  or  relations  can  be  made  adjustable,  as  in  the 
ploughs. 

The  old  woman’s  tooth,  or  “  router,”  is  used  for  planing  out 
the  bottoms  of  recesses,  the  depth  to  which  the  iron  stands  out 
from  the  face  of  the  stock  being  adjustable.  It  is  therefore  an 
exception  to  the  general  plane  design,  in  which  the  iron  stands  but 
very  slightly  out  from  the  face  of  the  stock,  inch,  inch,  or  less. 

There  are  so  many  different  kinds  of  planes  that,  though  they 
have  a  family  resemblance,  the  various  groups  require  to  be 
operated  differently,  if  the  best  results  are  to  be  secured.  Actually 
there  are  only  two  instances  in  which  a  plane  iron  is  employed  in 
the  same  fashion  as  a  chisel  is  used  in  paring — that  is,  with  the 


flat  face  in  exact  coincidence  with  the  face  of  the  work.  One  of 
these  is  the  familiar  spokeshave,  the  other  is  the  rounder  plane, 
used  for  rounding  up  rulers,  broom  handles,  and  other  long 
circular  rods,  the  iron  cutting  tangentially.  In  all  other  cases  the 
chisel  is  set  in  its  stock,  neither  parallel  nor  tangentially,  but  in 
such  a  way  that  its  cutting  face  makes  a  large  angle  ■with  the  face 
of  the  work.  And  it  does  not  matter  in  the  least  which  face  lies 
next  the  work,  whether  the  flat,  or  the  bevelled  one,  since  the 
power  of  control  no  longer  lies  with  the  chisel  itself,  but  is  trans¬ 
ferred  to  its  stock.  The  flat  face  may  be  downwards,  next  the 
stuff,  as  in  many  of  the  iron  planes,  or  it  may  be  uppermost,  as  is 
the  usual  practice.  In  the  first,  the  angle  of  setting  the  chisel  in 
its  stock  is  low,  or  acute ;  in  the  second,  it  is  steep. 

The  first  important  point  is  the  secure  fastening  of  the  iron,  so 
that  it  becomes  practically  one  with  its  stock.  It  must  not  rock 


40 


TOOLS. 


in  the  slightest  degree  on  its  seating  Fig.  38,  and  the  wedge 
must  bed  closely  down  at  h,  all  over  it.  In  this  way  the  tendency 
to  chattering  and  vibration  is  eliminated,  and  these  are  the 
principal  causes  of  choking.  Other  points  are,  to  see  that  the 
corners  are  removed  on  the  hone,  and  that  the  iron  is  either 
sharpened  straight  across,  or  with  the  slightest  possible  convexity, 
which  is  tested  by  standing  the  edge  of  the  iron  lengthwise  on  the 
face  of  the  stock,  and  noting  the  light  underneath.  An  iron  must 
not  be  in  the  slightest  degree  concave. 

When  one  begins  to  handle  planes,  the  first  trouble  that  arises 
is  that  the  shavings  choke  in  the  mouth,  between  the  iron  and 
the  stock.  This  is  more  apparent  in  the  trying,  and  smooth¬ 
ing  plane,  than  in  the  jack  plane.  The  first  impression  is,  there¬ 
fore,  that  the  mouth  is  too  narrow  to  permit  the  shavings  to  get 
away,  and  an  apprentice  will  not  infrequently,  unless  checked, 
cut  the  mouth  wider,  and  so  lose  two  or  three  years  of  wear.  But 
the  fact  is  soon  discovered  that  better  results  are  obtained  if  the 
amount  of  convexity  given  across  the  edge  of  the  iron  is  increased, 
and  thus  another  error  is  committed— that  of  making  the  irons  of 
trying  and  smoothing  planes  nearly  as  convex  as  those  of  the  Jack 

plane.  Then,  of  course,  they  are 
unfit  for  producing  true  surfaces. 
For  if  those  irons  be  sharpened 
straight  across,  and  only  just  the 
corners  rubbed  off,  they  will  operate 
as  freely  as  though  well  rounded,  pro¬ 
vided  other  matters  are  attended  to. 

The  rigidity  of  the  iron  a,  is 
increased  by  the  addition  of  the  top 
iron  B.  The  difference  between 
single  and  double  iron  planes  is 
most  marked,  and  this  is  due  largely 
to  the  fact  that  the  screwing-down 
of  the  top  iron  tightly  on  the  cutting- 
Fig.  39.  Fig.  40.  iron  stiffens  the  latter  so  much  that 

all  chance  of  chatter  is  absorbed 
thereby.  How  important  this  is  may  be  observed  by  noting  the 
difference  in  the  working  of  a  plane  when  the  top  iron  is  set  back 
from  to  yV  ioch  (Fig.  39),  and  when  it  is  brought  down  quite 
close  to  the  cutting  edge  (Fig.  40).  The  first  is  incompatible  with 


PLANES. 


4T 

the  production  of  the  finest  results  ;  the  latter  is  essential  thereto. 
In  working  on  soft  pine  the  coarse  setting  has  scarcely  any  evil 
results ;  but  it  becomes  most  marked  when  attempting  to  plane 
crooked  grain,  knots,  and  hard,  harsh  wood,  and  end-grain,  on 
which  it  is  impossible  to  produce  smooth  surfaces  except  with  a 
finely-set  top  iron. 

The  setting  of  the  top  iron  also  has  a  secondary  influence. 
It  coerces  the  severed  shaving  immediately  behind  the  cutting  edge, 
and  compels  it  to  bend  over  at  the  instant  of  severance.  We  re¬ 
marked  (p.  23)  on  the  distinction 
between  the  axe  that  cleaves  the  wood 
a  little  way  beyond  the  cutting  edge 
and  the  paring  chisel  that  removes  and 
cuts  up  a  fine  shaving,  the  first  action 
being  percussive,  and  the  second  purely 
cutting.  A  similar  distinction  occurs, 
but  in  a  less  marked  degree,  between 
the  single  and  the  double  iron.  Take 
a  .single-iron  jack  plane  (Fig.  41)  set 
coarsely,  and  note  the  kind  of  shavings  removed.  They  are  not 
curled  off  regularly,  but  appear  to  have  been  split  off  in  a  succession 

of  jerks,  the  stuff  being  divided  in  front  of 
the  actual  cutting  edge.  But,  using  a  finely- 
set  double  iron  (Fig.  42),  such  an  action  is 
not  apparent,  for  the  shaving  appears  to  be 
quite  unbroken. 

Fig.  42.  Anything  that  interferes  with  the  perfect 

controlling  action  of  the  top  iron  lessens  the 
efficiency  of  the  plane.  If  the  bedding  of  the  top  iron  is  not 
perfect  on  the  other,  the  plane  will  choke,  or  chatter.  If  its  edge 
is  not  parallel  with  the  cutting  edge  the  same  evils  will  be  induced. 
Even  the  greasy  dirt  that  accumulates  on  the  top  iron  will  tend  the 
same  way,  and  it  should  therefore  be  rubbed  off  with  glass-paper. 

As  yet  these  remarks  have  had  reference  only  to  the  good  or 
bad  action  of  those  planes  which  are  designed  for,  and  are  appro¬ 
priate  to,  the  class  of  work  upon  which  they  are  commonly  used. 
But  the  question  of  the  appropriateness  or  otherwise  of  a  plane  to 
its  work  raises  many  points  of  detail.  To  be  concise,  the  problem 
may^be  considered  from  three  points  of  view — the  question  of 
angles,  of  linear  guidance,  and  of  profiles. 


42 


TOOLS. 


The  remark  has  already  been  made  that  the  sweet  working  of 
planes  is  less  a  question  of  angles  than  of  keeping  them  in  good 
order.  Thus  the  iron  of  a  common  plane,  Fig.  38,  is  set  at  an  angle 
r,  of  45°  in  its  stock.  The  ground  bevel  makes  one  of  about 
20°  to  25'"  or  30°,  with  the  face  of  the  stock,  depending  on  the 
work  of  the  plane,  and  when  newly  ground  the  sharpening  angle  e 
is  not  very  sensibly  divergent  therefrom.  Yet  the  plane  continues 
to  work  sweetly  after  successive  re-sharpenings  until  at  last  the 
angle  will  be  reduced  to  5°  or  with  the  stock.  The  only 
thing  that  remains  constant  is  the  angle  of  top  rake — namely,  45°. 
Though  the  cutting  angle  is  always  increasing  as  the  plane-iron 
thickens,  and  the  clearance  angle  is  always  being  reduced,  yet  the 
tool  works  sweetly.  On  the  other  hand,  in  an  iron  plane  in  which 
the  iron  is  set  face  downwards  at  an  angle  of  about  15°  with  the 
face  of  the  stock,  the  clearance  never  changes  ;  but  that  of  top  rake 
and  of  cutting  always  increases  with  sharpening.  And  the  cutting 
angle  of  the  latter  usually  becomes  thicker  with  re-sharpening  than 
is  practicable  in  the  case  of  the  irons  of  the  wooden  planes,  for 
with  a  face  angle  of  15“,  and  a  grinding  angle  of,  say,  20°,  if  this  is 
gradually  increased  by  10°  to  15°  by  sharpening,  the  total  angle 
will  be  greater  than  that  which  is  possible  in  the  wooden  planes. 
The  foregoing  facts,  taken  as  a  whole,  explain  why  the  same  planes 
can  be  readily  used  for  the  hard  and  soft  woods,  unlike  the  cutting 
tools  for  metals,  which  are  generally  shaped  differently  for  different 
metals.  But  though  a  45°  of  angle  in  a  plane  iron  is  used  for 
both  classes  of  timber,  the  workman  makes  slight  differences,  as 
experience  dictates  when  working  in  one  or  the  other.  The 
differences  lie  chiefly  in  the  degree  of  setting  of  the  top  iron,  which 
is  finest  for  the  hardest  and  harshest  woods,  and  in  the  coarse  or 
fine  setting  outwards  of  the  cutting  iron,  for  removing  coarse  or 
fine  shavings  respectively.  In  the  moulding  planes  a  difference  is 
made  in  angle  for  hard  and  soft  woods,  the  irons  in  the  former 
being  set  at  55°  or  60°  instead  of  45°.  But  the  forms  of  these 
planes  are  much  less  favourable  to  sweet  cutting  than  are  those  of 
the  bench  planes,  for  reasons  which  will  be  noted  directly. 

The  angles  of  plane  irons  are  compared  with  the  action 
of  the  chisel  in  Figs.  43-45,  between  which  there  is  much 
analogy.  Shavings  are  coarse  or  fine,  one  difference  consisting  in 
the  fact  that  the  coarse  shavings  are  broken,  while  the  fine  ones 
are  not  perceptibly  so.  If  we  consider  the  action  of  a  chisel 


PLANES. 


43 


when  removing  coarse  and  fine  parings,  we  shall  see  a  marked 
difference.  In  the  first  case  the  parings  will  be  like  Fig.  43, 
broken  in  polygonal  forms ;  in  the  second,  Fig.  44,  they  will  be 
continuous,  and  regularly  curved.  The  same  effect  is  observable 
in  planes,  the  coarsely  set  single  iron  of  Fig.  41  breaking  up  the 
shaving,  the  finely  set  double  iron  of  Fig.  42  removing  it  as  a 
continuous  ribbon.  But  the  iron  in  Fig.  41,  if  set  ever  so  finely, 
would  not  remove  such  fine  shavings  as  Fig.  42  ;  neither  if  the 
latter  were  set  very  coarsely  would  it  chatter  so  much  as  the 
former.  Hence,  in  planes  the  addition  of  the  top  iron  is  necessary 
in  order  to  counteract  the  influence  of  the  angular  setting  in  the 
stock,  which  setting  being  a  departure  from  the  chisel  principle, 
tends  to  cause  chattering.  An  important  function  of  the  top  iron 
therefore  consists  in  the  diminution  of  vibration  of  the  cutting  iron, 
effected  by  increasing  the  rigidity  of  that  portion  of  the  plane. 
That  rigidity  is  the  main  essential,  rather  than  the  mere  breaking 
of  the  shaving,  is  borne  out  by  the  fact  that  iron  planes  are  the 


Fig-  43- 


most  rigid  of  all,  and  that  in  these,  single  irons  (see  P'ig.  45)  can 
be  used  without  chatter,  or  choking,  even  when  cutting  against 
the  grain,  and  on  harsh  stuff. 

In  Fig.  42,  showing  the  iron  of  an  ordinary  plane,  whose  face  c, 
is  set  at  an  angle  of  45°  with  the  face  of  the  stock ;  45°  does  not 
represent  the  cutting  angle,  for  a  is  the  angle  of  presentment  of 
the  tool  to  the  work.  It  is  that  included  between  the  narrow 
sharpened  facet  of  the  iron,  and  the  face  of  the  material,  ranging 
between  about  5°  and  10°  only — just  an  angle  of  relief,  and  no 
more.  The  other,  is  that  formed  by  the  first  grinding  of  the 
basil,  and  is  the  reserve,  so  to  speak,  which  is  drawn  upon  for 
sharpening.  The  top  face  r,  answers  to  the  bevel  therefore  of  a 
chisel,  and  the  sharpened  facet,  or  rather  the  sole  of  the  stock,  to 
its  face.  In  Fig.  45,  which  represents  the  mouth  of  an  iron  plane 
in  section,  the  bottom  angle  a,  is  increased,  being  about  20°, 
and  the  top  b.,  on  which  the  sharpening  takes  place  is  not  very 
different  from  that  of  the  first  example.  But  in  these  apparently 


44 


TOOLS. 


diverse  cases,  that  which  renders  the  plane  so  valuable  is  the 
guidance  afforded  by  the  stock,  without  which  it  would  not  be 
possible  to  remove  shavings  of  uniform  thickness,  that  is,  with 
chisels  alone,  held  at  the  same  angles  as  the  plane  irons. 

Our  second  point — that  of  linear  guidance — is  the  feature  that 
is  most  obvious  in  planes ;  in  all  its  degrees,  from  the  tiny  thumb- 
plane  of  4  in.  to  6  in.  long,  to  the  cooper’s  planes,  measuring  as 
many  feet.  In  another  form  we  have  the  planes  controllable  in 
sweeps,  known  as  compass  planes,  the  elementary  type  of  which  is 
the  spokeshave. 

Since  the  control  of  the  iron  depends  on  the  linear  guidance 
exercised  by  the  face  of  a  plane,  this  is  proportionate  to  the 
character  of  the  work  done.  Hence  the  reasons  why  the  planes 
which  are  used  for  making  close  joints,  whether  glued  or  not,  are 
always  the  longest.  The  common  jack  plane  is  never  employed 
for  this  purpose,  and  its  length  is  limited  to  from  14  in.  to  17  in. 
But  the  trying  plane  ranges  between  22  in.  and  26  in.,  and  when 
specially  long  joints  have  to  be  made,  jointers  are  used  from  28 
in.  to  30  in.  long,  while  the  cooper’s  jointer  of  5  ft.  to  6  ft.  is  an 
extreme  instance  of  specialisation.  Smoothing  planes,  rebates, 
moulding  planes  In  all  cases  measure  less  than  12  in.  in  length, 
for  there  is  no  question  of  very  accurate  jointing  in  most  of  these — 
that  is,  not  in  the  same  degree  in  which  it  applies  to  the  trying 
planes. 

However  accurate  the  face  of  a*  plane,  it  wears  with  service, 
and  therefore  it  is  periodically  “shot”  with  a  trying  plane  in  good 
order.  Jack,  trying,  and  smoothing  planes  are  treated  thus,  twice 
or  thrice  in  a  twelvemonth,  and  every  care  is  taken,  by  the 
assistance  of  straight-edges  and  winding  strips,  to  restore  the  faces 
to  perfect  accuracy.  To  maintain  permanence  of  form  is  the 
principal  reason  for  the  employment,  first  of  iron-soled  planes, 
and  then  of  planes  with  iron  stocks.  The  latter  may  be  of  the 
skeleton  form,  or  a  skeleton  may  be  filled  in  with  blockings  of  hard 
wood.  But  there  is  the  other  advantage  derived  from  iron 
planes,  due  to  their  rigidity,  and  by  virtue  of  which  they  work 
more  sweetly  in  hard,  harsh,  cross-grained,  and  stringy  woods  than 
those  having  stocks  of  wood. 

The  circular,  or  compass  planes,  are  used  for  concave  sweeps. 
The  simplest  form  is  a  smoothing  plane  with  a  sole  cut  convex 
lengthwise.  But  such  a  plane  is  not  well  adapted  for  any  sweeps 


PLANES. 


45 


which  are  of  much  flatter  radius  than  the  radius  of  the  sole.  The 
next  advance  is  to  insert  a  sliding  piece  in  the  front,  by  the 
adjustment  of  which  the  range  of  utility  is  increased.  In 
American  forms  the  sole  is  made  flexible,  consisting  of  a  thin 
strip  of  elastic  steel,  which  is  adjusted  to  any  required  curve  by 
means  of  a  thumb-screw.  Compass  rebate  planes  are  also 
employed,  and  in  some  cases  both  the  face  and  one  side  are 
sweeped. 

The  third  point  of  view  from  which  we  have  to  consider  the 
planes  is  that  of  their  profiles,  or  the  sectional  forms  of  their 
cutting  edges.  These  are  the  counterparts  of  the 
work  which  they  have  to  do.  In  the  trying  plane 
we  have  seen  that  the  edge  has  to  be  as  straight  as 
possible  if  close  joints  have  to  be  produced  by  it. 

In  the  jack  plane  a  good  deal  of  convexity  (Fig.  46) 
is  imparted  to  produce  a  penetrative  and  shearing 
cut,  in  which  its  primary  value  lies.  But  the  con¬ 
trolling  power  and  co-relation  of  the  plane  to  its 
work  is  seen  in  its  greatest  development  in  the 
numerous  moulding  planes.  The  labour  of  cutting 
a  strip  of  wood  into  any  moulded  form  by  means 
of  chisels  and  gouges  is  so  great  that  the  develop¬ 
ment  of  these  planes  was  an  early  necessity.  Possi¬ 
bly  the  “  hollows  ”  and  “  rounds  ”  preceded  the 
numerous  moulding  planes,  which  are  mostly  com¬ 
binations  of  hollows,  rounds,  and  flats.  Though 
these  are  superseded  in  modern  shops  by  the  moulding  machines, 
they  are  yet  used  in  the  small  country  shops,  and  on  jobbing  work. 

Knack  is  required  to  handle  some  of  these  planes  nicely — 
such  as  some  of  the  ogees,  quirk  ovolos,  torus,  beads,  and  sashes 
— because  the  combinations  of  curves  and  flats  are  such  that 
some  portions  of  the  irons  are  in  the  worst  possible  position  for 
cutting — in  fact,  in  some  localities  they  stand  perpendicularly  to 
the  work  instead  of  at  an  angle,  as  all  irons  should  do.  To  a 
slight  extent  this  is  counteracted  in  some  planes  by  setting  the 
stock  at  an  angle  to  the  work,  or  at  a  “  spring,”  in  order  to  lessen 
these  drawbacks  by  a  principle  of  averaging.  But  good  working 
mainly  depends  on  the  careful  way  in  which  they  are  sharpened, 
set,  and  used.  Particular  care  must  be  exercised  to  keep  the 
angles  keen  enough,  and  the  edge  profiles  of  the  iron  exactly  co- 


Fig.  46. 


46 


TOOLS. 


incident  with  those  of  its  wooden  stock.  These  planes  also  suffer 
from  the  disadvantage  that  they  have  single  irons  only,  and  are 
therefore  liable  to  chatter.  For  this  reason  the  bedding  of  the 
iron  on  its  stock,  and  the  close  fitting  of  the  wedge  are  very 
important  points.  The  planes  are  also  rather  hard  to  work,  and 
drag  somewhat,  especially  in  wide  and  deep  mouldings.  Some  of 
these  planes,  like  the  plough,  are  used  for  cutting  deep  grooves. 


and  though  perpendicular  edges  are  present,  they  are  not  actually 
cut  by  the  iron,  and  here  friction  and  dragging  occur. 

Some  of  the  profiles  of  these  planes  are  grouped  in  Figs.  47 
to  50.  Figs.  47  are  the  irons  of  rounds,  and  hollows,  the  sections 
of  which,  going  by  numbers,  are  shown  in  Fig.  48.  Fig.  49  is  the 
iron  of  the  plough  for  grooving — eight  irons  of  different  widths 

forming  a  set  for  a  plane. 
Fig.  50  is  the  iron  of  one 
form  of  beading  plane. 
Besides  these  there  are 
planes  to  correspond  with 
various  mouldings  for  sash 
bars,  and  strips,  to  enume¬ 
rate  which  would  be  hardly 
possible  here.  Ovolos, 
quirk  ovolos,  ogees,  astra¬ 
gals,  reeding  tools,  sash 
tools,  air-tight  planes  for 
making  tongued  and  grooved  joints,  blisters,  and  others.  Rebate 
planes  occur  in  various  types,  straight,  and  skew  mouthed  (Fig.  51), 


Fig.  51- 


PLANES. 


47 


and  side  rebates.  Chamfer  planes  form  another  group,  and  so  do 
chariot,  and  bull-nose  planes,  for  cutting  up  close  to  a  shoulder. 

The  iron  planes  have,  to  a  large  extent,  invaded  the  pro¬ 
vince  of  those  with  wooden  stocks,  some  firms  making  a 
speciality  of  their  manufacture.  They  occur  in  the  following 
groups :  jack,  trying,  and  smoothing ;  the  latter  being  commonly 
termed  block  planes ; — bull-nose,  rebate,  circular-soled,  tonguing 
and  grooving,  routers,  hollows,  and  rounds,  beading,  ploughs, 
universal,  and  spokeshaves. 

Fig.  52  shows  a  lever  block  plane.  The  lever  a  takes  the  place 
of  the  usual  wedge.  It  is  pivoted  at  a,  and  turning  the  milled 
head  and  screw  b,  pinches  it  on  the  top  of  the  iron  at  b.  Instead 
of  tapping  the  iron  inwards  or  outwards,  it  is  moved  slightly  by 
the  lever  c,  hinged  at  c,  and  having  serrations  on  its  upper  face 
to  engage  with  serrations  on  the  lower  face  of  the  iron  at  d. 


/4 


Fig.  53- 


Fig.  52. 


A  different  type  of  iron  plane  is  shown  in  Fig.  53.  a  is  the 
base  into  which  the  handle  b  is  screwed.  The  iron  c  is  double, 
and  the  cap  d  holds  the  iron  down.  The  adjustment  of  the 
latter  is  effected  by  the  milled  head  e  operating  a  lever  entering 
into  a  slot  in  the  iron.  The  portion  f,  the  frog,  can  be  adjusted 
to  close  up  the  opening  of  the  mouth  if  wear  occurs. 

No  plane  is  easily  handled  by  the  beginner.  The  art  con¬ 
sists  first  in  exercising  the  most  perfect  control  over  the  tool, 
instead  of  allowing  it  to  wabble  about  all  over  the  stuff.  It  is 
true  that  the  workman  appears  to  hold  it  very  slackly  and  easily ; 
but  he  has,  nevertheless,  a  perfect  grip  on  it,  so  that  it  does 
not  tip  up  at  the  beginning  and  termination  of  every  stroke,  nor 
slip  over  the  knots,  nor  remove  shavings  from  the  wrong  places. 

All  planes,  except  the  tiny  thumb  planes,  require  to  be  gripped 
in  both  hands.  The  trying  and  the  jack  planes  are  grasped  by 
their  handles  with  the  right  hand,  while  the  left  is  spread  over 


8 


TOOLS. 


the  top  of  the  body  of  the  plane  near  the  front  end,  slightly 
gripping  the  sides  also.  The  smoothing  planes  and  all  the 
rebates  and  moulding  planes  and  their  cognate  forms,  which 
have  no  handles,  are  gripped  in  the  rear  with  the  right  hand, 
the  heel  of  the  hand  exercising  a  thrust  on  the  stock  downwards 
and  forwards,  while  the  left  hand  steadies  the  plane  in  front. 

The  degree  of  pressure  transferred  from  the  body  to  a  plane 
varies  much,  being  very  considerable  when  roughing  down. 
Most  planing,  like  sawing,  taxes  the  muscles,  though,  when 
accustomed  to  it,  one  can  occupy  a  whole  day  in  either  task 
without  feeling  unusually  tired  ;  but  it  exhausts  the  beginner. 
The  muscles  of  the  arms,  and  a  portion  of  the  weight  of  the 
body  are  both  brought  to  bear  upon  the  plane,  and  the  proper 
degree  of  force  exercised  is  graduated  in  a  nearly  unconscious 
and  instinctive  manner. 

The  guidance  of  the  planes  usually  depends  on  the  skill  of 


Fig.  55- 


Fig.  54. 


the  operator.  All  those  in  which  the  edges  of  the  irons  lie 
inside  the  stock,  as  in  the  jack,  trying,  and  smoothing  planes, 
require  no  control  save  that  of  the  workman,  except  when  used 
on  a  shooting  board  (Fig.  54),  or  a  mitre  board  (Fig.  55),  for 
planing  edges  and  ends.  But  when  the  irons  come  out  flush 
with  edges,  as  in  the  rebates,  or  when  they  project,  as  in  the 
plough,  or  when  a  planed  edge  has  to  be  worked  by,  as  in  the 
beads  and  kindred  forms  of  moulding  planes,  they  are  coerced, 
either  by  the  edge  of  a  strip  of  wood  tacked  upon  the  face  of 
the  work,  in  the  exact  position  where  a  shouldered  portion  is  to 
be  formed,  as  when  rebating,  or  by  a  fence,  which  is  adjustable, 
as  in  the  plough,  or  by  a  fixed  fence,  as  in  the  beads,  fili.sters, 
&c.  In  planing  narrow  strips,  with  rounds,  or  hollows,  the 
angle  board  (Fig.  56)  coerces  the  stuff  sideways,  preventing  it 
from  slipping  about.  The  rounds,  and  hollows,  and  many  others 
are  controlled  only  by  the  fingers  of  the  left  hand.  Tools  of 


PLANES. 


49 


these  classes  are  only  suitable  for  cutting  with  the  grain.  Some 
are  used  also  for  cutting  across,  but  then  a  saw-kerf  must  be 
made  to  sever  the  grain,  as  in  rebating. 

Another  point  is,  that  the  skilful  man  does  not  need  to  check 
the  results  of  his  work  nearly  so  often,  or  so  much,  as  one  who 
is  unskilled.  When  planing  a  level  surface,  the  latter  timidly 
resorts  to  straight-edge  and  winding-strips  long  before  the  surface 
is  approaching  completion ;  the  other  feels  by  the  nature  of  the 
contact  between  the  plane  and  the  wood  how  the  work  is  pro¬ 
gressing,  and  uses  the  edge  of  the  plane  itself  as  a  rough 
straight-edge — tipping  the  tool  to  a  slight  angle,  and  glancing 
under  the  edge  in  the  intervals  of  every  few  strokes.  And  yet 
he  arrives  at  the  desired  result  quickly.  If  he  has  much  to 
slog  off,  he  does  not  plane  in  an  unvarying,  straightforward 
fashion,  but  alternates  these  cuts  between  cross  and  diagonal 
ones,  which  are  of  the  nature  of  shearing ;  so  not  only  reducing 
material  with  the  minimum  of  labour,  but  also  getting  close 


Fig-  56. 


approximation  to  truth  across  the  board.  As  also  the  jack  plane 
removes  stuff  most  rapidly,  its  employment  is  continued  until 
the  fine  finishing  of  the  trying  plane  becomes  quite  necessary. 
A  beginner  will  commence  working  with  the  trying  plane  too 
soon,  and  so  waste  time  in  removing  a  quantity  of  material  that 
could  have  been  taken  off  in  one-fourth  the  time  with  the  jack 
plane. 

Further,  with  a  view  to  preserve  the  edges  as  long  as  possible, 
and  so  avoid  the  need  of  too  frequent  sharpening,  the  experienced 
man  relieves  the  cutting-iron  of  the  weight  of  the  plane  on  its 
backward  stroke,  so  preventing  friction  between  it  and  the  face 
of  the  board.  The  harsher  and  more  gritty  the  stuff,  the  more 
desirable  is  this  instinctive  precaution.  Before  roughing-down 
dirty  stuff  with  the  jack  plane,  too,  the  careful  man  brushes  the 
outside  with  card  wire,  to  remove  the  dirt  and  grit  before  using 
the  plane  on  it,  and  then  he  sets  the  iron  coarsely  in  order  to  get 
well  beneath  the  surface  in  the  first  cuts,  instead  of  allowing  the 

D 


5° 


TOOLS. 


dirt  to  grind  the  edge  off  the  plane,  just  as  the  iron-turner  and 
machinist  get  below  the  skin  at  once. 

When  testing  the  truth  of  planed  faces,  both  straight-edges, 
and  winding-strips  are  requisitioned.  A  straight-edge  alone  will 
serve  the  functions  of  both,  because  when  held  diagonally  across 
a  board,  if  the  straight-edge  shows  true  faces  in  both  diagonal 
directions  the  face  is  out  of  winding,  the  result  being  the  same  as 
though  tested  with  parallel  winding-strips  at  the  ends.  But  this 
method,  though  quite  suitable  for  short  pieces  of  stuff,  say  not 
exceeding  2  ft.  to  3  ft.  in  length,  is  not  so  suitable  as  the  other 
for  long  wide  boards,  because  the  strips  magnify  any  error  due  to 
their  length,  the  latter  being  considerably  longer  than  the  width  of 
a  board.  Of  course,  in  trying  the  truth  of  boards  it  is  not  enough 
to  lay  the  straight-edge  on  them.  That  is  good  enough  during 
the  earlier  stages,  but  later,  chalk  must  be  rubbed  on  the  straight¬ 
edge,  and  transferred  by  very  slight  pressure  and  slight  endlong 
movement  to  the  face  being  planed.  This  visibly  indicates  by  its 
transference  or  not,  what  portions  of  the  face  are  high  or  low,  and 
where  the  material  requires  removal.  The  straight-edge  is  tried 
crossways  at  intervals  of  every  few  inches,  and  a  long  straight-edge 
is  also  tried  lengthwise;  besides  which,  the  winding-strips  are 
tried  on.  Sighting  down  the  latter,  the  edge  of  the  farther  one  is 
more  clearly  seen  if  the  face  that  lies  next  the  edge  is  whitened 
with  chalk. 

Always  the  first  step  is  to  plane  one  face  perfectly  true,  and 
gauge  the  thickness  from  that  by  which  to  plane  the  second 
face.  As  a  board  is  seldom  quite  straight  across  when  taken  from 
the  rack,  the  concave  face  is  better  to  begin  work  on  than  the 
convex,  because  the  latter  would  be  pressed  down,  and  sprung  by 
the  weight  of  the  plane.  But  it  is  always  better  to  “jack”  over 
both  sides  before  beginning  to  finish  either  face ;  or  if  this  can  be 
done  a  few  days,  or  even  a  few  hours,  before  planing  to  thick¬ 
ness,  it  is  better,  because  there  is  less  risk  of  the  board  warping 
subsequently. 

When  planing  end  grain,  the  expert  workman  does  not  let 
the  plane  tip  over  the  end  and  split  the  stuff  out ;  but  he  either 
chamfers  the  extreme  end  with  a  chisel,  or  else  planes  a  few 
strokes  from  each  end  alternately,  relieving  the  plane  just  as  it 
comes  to  the  termination  of  its  cut.  When  practicable,  he  will 
plane  ends  and  edges  on  the  shooting-board  (Fig.  54,  p.  48),  rather 


PLANES. 


5^ 


than  in  the  vice,  because  with  the  use  of  the  shooting-board  there 
is  no  necessity  to  try  the  truth  of  the  edge  with  the  square,  re¬ 
latively  to  the  face  of  the  board. 

A  good  workman  will  not  allow  one  plane  to  usurp  the  functions 
of  another,  nor  expect  the  smoothing  plane  to  produce  a  true 
surface  like  the  trying  plane,  nor  use  the  latter  merely  to  dress  off 
joints  flush,  or  to  clean  a  dirty  surface  previous  to  glass-papering, 
or  to  round-up  an  edge.  Nor  will  he  attempt  to  round-up  any  con¬ 
siderable  quantity  of  work  with  a  smoothing  plane  when  hollow 
planes  are  available. 

To  set  an  iron  in  its  stock  suitably  for  different  classes  of  work 
is  not  quite  so  easy  as  it  appears.  Beginners  knock  their  planes 
about  sadly  in  getting  the  irons  in  and  out,  and  in  correcting 
their  setting.  No  very  hard  blows  need  ever  be  dealt.  The 
most  trying  work  to  a  plane  is  the  presence  of  hard  knots  in  soft 
wood — those  in  spruce,  for  example ;  and  contact  with  these  will 
often  cause  a  loosely  fitting  iron  to  start  backwards,  so  that  in  such 
cases  the  wedge  should  be  driven  more  tightly  than  under  normal 
conditions ;  but  to  drive  a  wedge  habitually  tight  only  springs  the 
stock,  without  holding  the  iron  any  better. 

The  setting  of  an  iron  is  accomplished  by  bringing  the  face  of 
the  plane  in  line  with  the  ey«  in  a  good  light,  and  sighting  down, 
when  the  exact  projection  of  the  iron  beyond  the  face  of  the  stock 
is  readily  detected  by  the  eye,  and  also  whether  it  is  parallel  cross- 
ways.  If  it  projects  to  a  greater  distance  towards  one  side  than 
the  other,  the  edge  of  the  iron  beside  the  wedge  is  tapped  with  the 
hammer  on  the  side  where  the  projection  is  too  full.  If  it  stands 
out  too  far  all  across,  the  top  of  the  plane  stock  is  lightly  tapped 
with  the  hammer,  in  jack  and  trying  planes,  to  start  the  iron 
upwards  by  reaction.  In  the  smoothing  and  moulding  planes, 
the  rear  end  is  struck.  A  tap  on  the  top  end  of  the  iron  sets  it  out. 
When  adjustments  are  all  completed,  a  final  tap  or  two  is  given 
on  the  wedge. 

Damage  to  planes  is  caused  by  the  hammering  of  the  stock 
to  effect  the  removal  of  the  iron.  In  trying,  and  jack  planes, 
this  is  done  on  the  top  front  face  with  the  hammer  held  in  the 
right  hand,  the  left  grasping  the  side  of  the  plane,  and  the  thumb 
being  inserted  in  the  hollow  of  the  wedge,  to  steady  it,  and  con¬ 
trol  the  results.  In  smoothing  planes  a  sharp  blow  is  delivered  at 
the  hinder  end ;  in  the  moulding  planes  under  the  knob  of  the 


52 


TOOLS. 


wedge.  As  these  blows  are  repeated  so  frequently,  they  must  be 
delivered  quite  flat  and  dead,  in  order  not  to  bruise  and  damage 
the  wood  overmuch.  A  little  knob  is  often  glued  into  a  centre- 
bit  hole  in  the  top  of  jack  and  trying  planes  to  receive  these 
blows.  When  wedges  are  being  driven  in,  they  should  not  be 
bruised  and  burred  over;  partly  with  a  view  to  prevent  this,  their 
edges  are  chamfered. 

To  maintain  planes  in  good  order,  fit  for  producing  clean  and 
smooth  surfaces  on  soft  straight-grained  woods,  is  not  so  difficult 
as  when  they  have  to  work  against  the  grain,  and  over  knots,  and 
on  stringy  harsh  stuff.  In  some  of  these  cases  it  is  better  to  have 
an  iron  sharpened  rather  thickly  than  thin,  and  it  will  usually 
have  to  be  set  very  finely  to  remove  a  mere  scrape ;  in  fact,  in 
such  cases  the  plane,  though  sharp,  will  do  better  if  its  action 
approximates  to  scraping,  because  it  will  not  then  have  so  great  a 
tendency  to  tear  up  the  harsh,  coarse  grain.  When  planing  sappy 
stuff  the  mouth  is  very  liable  to  choke,  and  the  tool  works  with 
much  friction.  A  liberal  application  of  sweet  oil  to  the  sole  of 
the  plane  is  very  helpful  in  this  case. 

In  sharpening  moulding  planes  much  care  is  necessary  in 
order  to  preserve  their  profiles  exactly.  The  irons  should  be 
ground  on  very  small  emery  wheels,  or  they  are  filed  sometimes 
with  new  finely- cut  files ;  they  are  sharpened  with  gouge  slips.  In 
using  any  of  these  planes  it  is  difficult  to  start  properly.  Some, 
like  the  sash  fibsters,  have  adjustable  guides  or  fences  to  be  held 
against  the  side  of  the  work.  So  have  the  beads,  the  ploughs, 
the  chamfer  planes,  and  others.  In  the  rounds,  and  hollows  the 
workman’s  hands  afford  the  only  control.  In  the  rebate  planes  it 
is  usual  to  nail  or  clamp  a  strip  down  to  the  work  as  a  guide.  In 
depth  gauging  there  are  stops,  as  those  used  for  sash  fibsters  and 
for  the  ploughs,  and  these  are  adjustable  with  screws,  so  that  we 
get  a  good  many  complications  in  moulding  planes.  But  in  a 
large  degree  interest  in  these  has  diminished  since  mouldings  are 
stuck  by  machinery,  and  there  are  many  younger  joiners  who  have  * 
never  had  a  chance  to  use  such  planes,  and  have  had  no  need  to 
add  them  to  their  kit. 

The  wear  and  tear  of  planes  is  due  to  the  wearing  of  the  iron, 
of  the  sole,  and  of  the  removal,  and  resetting  of  the  iron.  The 
first-named  has  the  effect,  in  most  cases,  of  increasing  the  width 
of  the  mouth,  the  exception  being  in  the  case  of  those  irons  which 


PLANES. 


53 


are  parallel.  In  the  tapered  iron,  the  wearing-down,  due  to 
regrinding,  brings  the  thinner  portion  down  to  the  mouth,  and  so 
increases  the  width  of  the  latter.  But  the  chief  wear  to  planes  is 
that  due  to  the  constant  friction  of  the  face,  which  causes  it  to 
get  out  of  truth,  to  correct  which  the  face  has  to  be  “  shot,”  or 
planed  afresh,  so  widening  the  mouth.  After  several  years  this 
width  becomes  so  great  that  a  mouth-piece  has  to  be  fitted  across. 

In  selecting  planes,  the  grain  of  the  wood  is  a  matter  of  much 
importance.  Straight  grain  of  course  is  looked  for ;  and  heart 
wood  must  be  rejected.  A  hard  quality  of  timber,  cut  from  the 
outer  layers  of  the  tree,  is  the  best ;  the  latter  being  apparent 
by  the  ring  segments  having  scarcely  any  convexity.  The  silver 
grain  also  must  run  perpendicularly  to  the  face  of  the  plane, 
and  not  diagonally.  A  stock  selected  thus  has  the  best  wearing 
quality,  and  is  less  liable  to  warp  than  one  in  which  the  contrary 
conditions  are  present. 

All  plane  stocks  are  made  of  beech,  excepting  the  smallest 
thumb  planes,  and  spokeshaves,  and  the  quirks,  and  fences  of 
some  of  the  moulding  planes,  ploughs,  &c.,  which  being  subject 
to  much  wear  are  of  box.  To  preserve  a  new  plane,  a  good  plan 
is  to  harden  its  face  by  saturating  it  for  two  or  three  days  in  raw 
linseed  oil,  and  rubbing  oil' all  over  elsewhere,  applying  it  thickly 
and  afresh  as  it  sinks  into  the  grain.  Also  after  shooting  a  plane, 
the  face  must  be  saturated  with  oil  to  harden  it,  and  to  cause  it 
to  work  more  sweetly. 


CHAPTER  IV. 

Hand  Chisels  and  Allied  Forms  for  Metal  Working. 

The  Cold  Chisel — Cutting  Angles — Shape — Breadth — Method  of  Use — The 
Cross-cut  Chisel — Diamond  Point — Cold  and  Hot  Setts — and  Gouges — 
Setts  for  the  Steam  Hammer — Nicking  Chisel — Drifts  or  Broaches. 

These  chisels  are  not  nearly  so  numerous  as  those  of  the 
wood  worker.  They  are  simple  in  character,  and  yet  a 
very  slight  difference,  not  to  be  appreciated  save  by  those 
who  know  them  well,  will  make  all  the  difference  in  their  effective, 
or  non-effective  action.  The  roughing-out  tool  par  excellence  of 
the  fitter,  is  the  cold  chisel  in  its  various  types.  The  cutting  edge 
of  the  typical  “chipping”  or  “cold”  chisel  (Fig.  57,  a)  gives  60° 


n 

1  fl 

.  1 

D 

A  ' 

li 

I  \ 

1 

J 

Fig-  57- 


cutting  angle,  but  it  may,  and  does  vary  several  degrees  on  each 
side  of  this,  not  only  for  different  materials,  but  for  materials  of 
the  same  character.  The  practical  rule  to  lay  down  is,  that  the 
harder  the  material,  the  more  obtuse  the  cutting  angle ;  the  softer 
the  material,  the  more  acute  will  it  be.  This  of  course  is  a  neces¬ 
sary  modification,  not  alone  in  the  case  of  chisels,  but  also  of  all 
cutting  tools,  not  because  an  obtuse  edge  cuts  better  than  an  acute 
one,  but  simply  because  it  endures  better. 


HAND  CHISELS  FOR  METAL  WORKING.  55 


A  little  practice  soon  demonstrates  the  best  angle  for  a  chisel 
for  any  particular  kind,  or  grade  of  metal.  Hard,  harsh  metal  will 
rapidly  spoil  the  chisel  edge,  and  then  the  remedy  is  obvious — 
grind  it  thicker.  But  a  moderately  thin  chisel  will  cut  soft  iron 
rapidly,  and  without  losing  its  edge,  and  one  thinner  still  will  work 
gun  metal,  and  brass  with  ease.  This  is  really  the  ultimate  test, 
the  cutting  of  the  largest  quantity  of  any  given  material  with  the 
least  expenditure  of  labour,  and  the  most  lasting  permanence  of 
edge. 

The  tool  is  held  approximately  at  the  angle  in  which  one  facet 
comes  nearly  parallel  with  the  face  of  the  material  being  operated 
upon,  giving  the  smallest  possible  angle  of  relief.  A  slight  round¬ 
ing  is  imparted  to  the  edge  in  the  transverse  direction,  the  object 
of  which  is  to  prevent  risk  of  the  corners  catching  in  the  material, 
which  would  draw  the  chisel  out  of  parallel.  Most  wide  chisels 
are  ground  thus  more  or  less  rounding,  though  sometimes  straight, 
but  never  hollow ;  not  much  rounding,  however,  is  given,  else  the 
chipped  surface  would  present  a  series  of  furrows. 

The  breadth  of  the  chisel  has  an  influence  upon  its  action. 
For  steel,  and  wrought  iron,  a  narrow  chisel  is  preferable  to  a 
wide  one,  because  they  are  of  a  close  solid  texture,  and  require  a 
considerable  application  of  force  to  effect  the  removal  of  chips 
therefrom.  But  the  more  crystalline  cast  iron  and  brass  are 
more  suitably  attacked  with  wider  chisels,  which  have  less  tendency 
to  dig  in,  and  to  tear  up  the  material  than  the  narrower  ones.  This 
again  is  not  a  hard-and-fast  rule,  since  both  wide  and  narrow 
chisels  are  used  indiscriminately  on  all  grades  of  metal.  But 
the  principle  laid  down  is  nevertheless  a  correct  one.  A  good 
deal  will  depend  on  the  force  of  the  blows,  the  depth  of  cut,  and 
the  amount  of  material  attempted  to  be  removed. 

To  use  the  chisel,  hold  it  near  its  head  in  order  to  afford 
steadiness  of  grasp,  stand  in  an  easy,  unconstrained  posture,  not 
hugging  the  chisel  too  closely,  and  deliver  the  blows  from  the 
shoulder.  The  cutting  edge  of  the  chisel  is  to  be  kept  pressed 
against  the  cut,  and  the  surface  is  to  be  reduced  as  evenly  as 
possible,  to  lessen  the  subsequent  labour  of  the  file.  Finishing 
cuts  will  be  taken  with  quicker  and  lighter  blows  than  the  roughing 
cuts. 

When  reducing  a  surface  of  large  area,  the  labour  can  be 
lessened,  and  better  results  obtained  by  first  cross-cutting  the 


56 


TOOLS. 


surface  all  over  with  the  cape,  or  cross-cut  chisel  (Fig.  57,  b).  A 
series  of  narrow  grooves  parallel  with  each  other  is  cut  with  this 
over  the  surface,  and  the  material  removed  from  between  with 
the  ordinary  chisel.  The  same  chisel  is  used  as  a  “  sett  ”  for 

nicking  pipes,  or  plates  preparatory  to 
severance. 

i  The  economic  importance  of  chip¬ 
ping  has  considerably  diminished  in 
I  the  workshops  during  the  present 
generation,  owing  to  the  wider  em¬ 
ployment  of  planing,  shaping,  and 
milling  machines.  There  is,  com¬ 
paratively  speaking,  little  call  now  for 
skill  in  chipping,  except  in  the  case  of  repairs,  and  of  work  too 
bulky  to  be  put  under  the  machines.  To  many,  therefore,  the  chip¬ 
ping  and  filing  of  a  large  surface  true,  especially  if  that  surface  be 
awkardly  situated,  as  for  instance  a  slide  valve  face  enclosed 
within  the  sides  of  its  steam  chest,  presents  a  not  too  easy  task. 

Fig-  57)  c,  is  a  diamond  point,  one  of  the  setts,  used  for 
nicking  metal  which  has  to 
be  severed,  and  also  for 
cutting  grooves.  Its  re¬ 
semblance  to  the  vee  chisels 
of  the  carver  (p.  33)  will 
be  apparent,  the  difference 
between  the  two  being  one 
of  thick,  and  thin  cutting 
angles.  Fig.  57,  d,  is  a 
narrow  round  nose,  also 
one  of  the  setts,  corre¬ 
sponding  with  the  wood¬ 
worker’s  gouge ;  while  Fig. 

57,  E,  is  a  wider  gouge,  con¬ 
cave  on  the  face,  also  termed 
a  cow-mouthed  chisel. 

These  tools  are  used  in  several  metal-working  trades,  by  fitters 
chiefly,  but  also  by  smiths,  and  boilermakers,  on  forgings  and 
plated  work,  as  well  as  on  castings. 

The  next  group  is  for  forged,  and  plated  work,  the  cold  and 
hot  chisels  or  setts  being  held  to  the  work,  and  struck  with  sledges. 


A 


^  — 
8 

- V _ 

Lj 

C 

Fig.  59- 


Fig.  58. 


ITAN'D  CHISELS  FOR  METAL  WORKING.  57 


I 


Fig.  58,  A,  is  the  cold,  and  Fig.  58,  b,  the  hot  sett,  the  difference 
between  the  two  being  that  of  angle  only,  the  latter  being  thinner 
than  the  former,  a  would  entail  unnecessary  labour  in  severing 
hot  metal,  while  b  would  not  retain  its  edge  long  in  cold  metal. 
Fig.  58,  c,  is  the  gouge,  or  hollow  sett,  made  also  for  hot  and  cold 
metal,  and  in  various  curvatures,  and  singly  as  well  as  doubly 
bevelled.  These  are  handled  with  rigid  rods  of  ash. 

The  next  group  fulfils  similar  functions,  but  they  are 
used  chiefly  with  power  hammer  work.  Fig.  59,  a,  is  a 
sett  made  thick,  and  thin,  for  cold,  and  hot  metal.  Fig. 

59,  B,  is  a  hot  gouge  sett  handled  like  the  previous  one. 

Its  function  is  severing  or  dressing  ends  w^hich  are  to  be 
bossed,  instead  of  cutting  facets  to  produce  polygonal 
outlines. 

Fig.  59,  c,  is  a  very  obtuse-angled  chisel  which  operates 
as  a  nicker  only,  setting  in  round  a  rod  under  the  hammer 
preparatory  to  severance.  It  is  used  on  hot,  or  cold  bars. 

Drifts  are  true  chisels.  Some  operate  by  their  ends  only,  but 
most  are  serrated  (Fig.  60).  They  both  cut,  and  shear,  and  are 
used  to  finish  holes  that  have  been  roughed  out  with  drills,  or 
chisels.  They  are  employed  both  in  blind,  and  thoroughfare 
holes,  finishing  accurately  and  to  uniform  dimensions.  They  are 
used  by  hand,  or  in  a  machine.  In  America  they  are  termed 
broaches. 


Fig.  60. 


CHAPTER  V. 


Chisel-like  Tools  for  Cutting  Metal  by  Turning, 

Planing,  &c. 

Roughing  and  Finishing  Type — Roughing  Tools — Finishing  Tools — Parting 
Tools— Inside  Tools — Tools  for  Planer  and  Shaper — Cranking — Overhang 
—  Stiffness  of  Tool  and  Support  —  Roughing  and  Finishing  Tools  — 
Straightforward  Tools  —  Cranked  Tools  —  Broad  Finishing  —  Slotting 
Tools. 

T''HE  principal  types  of  these  tools  are  shown  in  Figs.  6i  to 
65.  They  are  mainly  divisible  in  two  groups — roughing, 
and  finishing.  On  some  kinds  of  work  there  is  but  one 
type  practicable — the  finishing,  which  combines  the  two  functions. 
The  angles  of  tools  that  operate  on  the  same  materials  are  varied 
according  to  whether  they  are  employed  for  removing  material  in 
quantity,  or  for  finishing  by  scraping.  In  the  latter  case  they 

have  little  or  no  top  rake,  the  top 
face  being  normal,  or  nearly  so,  to 
the  surface  of  the  work.  It  is  also 
essential  to  the  highest  smoothness 
of  finish  that  the  edge  be  broad, 
and  straight.  The  angles  of  scraping 
tools  are  nearly  alike  for  all  metals 
and  alloys,  differing  in  this  respect 
from  the  roughing  tools. 

Fig.  61  is  the  commonest 
kind  of  roughing  tool  for  lathe, 
planer,  or  shaper,  and  if  clamped  in  a  bar,  for  the  slotting 
machine  also.  A  tool  used  for  the  same  work  is  prismatic  in 
form,  instead  of  being  round-nosed,  being  slightly  easier  to  grinds 
As  a  rule,  to  which  there  are  numerous  exceptions,  the  roughing 
tools  are  round-nosed,  the  advantage  being  that  they  possess 
penetrative  capacity  in  a  large  degree.  And  because  the  correct 
cutting  angle  only  occurs  at  that  portion  of  the  tool  d,  which 


TOOLS  FOR  CUTTING  METAL. 


59 


projects  most,  and  in  a  diminishing  degree  round  the  curve,  until 
at  E  E  there  would  be  no  top  rake  at  all,  this  limits  the  useful 
work  done  when  deep  cutting  is  attempted,  and  explains  the 
advantage  possessed  by  right  and  left  handed  roughing  tools,  in 
which  the  point  of  highest  projection  and  greatest  rake  corre¬ 
sponds  with  that  portion  of  the  work  being  cut  where  the  pene¬ 
tration  is  deepest.  Four  such  tools  are  shown  in  Fig.  62,  in 
pairs.  The  right,  and  left  hand  tools  at  a  differ  from  straight¬ 
forward  ones  in  the  method  of  grinding  the  top  rake — top  side 
rake  in  these  cases.  Those  at  b  differ  in  being  bent  round,  the 
grinding  of  the  top  faces  being  then  normal  to  the  centre  line  of 


Fig-  63. 


the  bent  part.  The  arrows  indicate  the  direction  of  movement 
of  the  tools,  and  c  c  shows  the  direction  of  the  top  side  rake. 

Fig.  63,  A,  shows  a  broad  finishing  tool  in  plan,  which  is  used 
with  coarse  sliding  feeds,  but  only  for  removing  shallow  chips. 
The  amount  of  top  rake  in  these  is  variable,  but  is  generally 
slight,  ranging  from  zero  to  10°  or  15°.  Fig.  63,  b,  is  the  spring 
tool,  used  for  fine  finishing,  with  a  mere  scrape.  The  action  of 
this  tool  can  be  better  understood  by  a  reference  to  the  planer 
tool  (Fig.  64),  the  point  of  which  is  brought  back  somewhere  about 
in  line  with  the  back  of  the  tool  shank,  in  order  to  prevent  risk 
of  the  cutting  edge  digging  in,  in  consequence  of  the  spring  of 
the  planer  rail,  or  of  the  overhanging  of  the  end  of  the  tool.  But 


6o 


TOOLS. 


Fig.  64. 


for  the  inconvenience  of  the  arrangement,  it  would  be  better  to 
mount  the  planer  tool  behind,  instead  of  several  inches  in  front 
of  the  rail.  With  the  tool  shaped  as  in  Fig.  64,  it  cannot  dig  in, 
even  though  it  should  spring  back,  because  the  point  would  be 
immediately  thrown  olf  the  work.  For  the  same 
reason  a  turning  tool  should  not  be  set  above  the 
centre  of  the  work,  but  level,  as  in  Fig.  61.  So, 
too,  if  the  spring  tool,  Fig.  63,  b,  meets  with  an 
obstacle,  it  yields,  and  will  not  dig  in.  The  cut 
becomes  analogous  to  a  drawing  cut,  as  distin¬ 
guished  from  a  pushing  cut.  But  spring  tools  are 
not  suitable  for  working  to  fine-gauged  dimensions  ; 
they  simply  impart  a  smooth  finish,  serviceable  in 
work  of  an  average  character. 

Tools  for  parting  off  (Fig.  63,  c)  have  clearance 
both  behind  and  below.  Being  generally  very  thin  at  the  cutting 
end,  this  is  commonly  reduced  from  a  bar  of  greater  width,  in 
order  to  afford  sufficient  width  and  rigidity  for  clamping  in  the 
tool-holder.  Such  tools  are  also  in  some  cases  required  to  be 
right  and  left  handed.  The  same  tool  generally  serves  for 
roughing  and  finishing,  but  knife-edge  or  side  tools  (Fig.  65,  a), 
right  and  left  handed,  straightforward,  as  shown,  or  bent,  are  used 
for  facing  an  end,  following  the 
parting  tool  before  a  piece  is 
actually  cut  off,  as  in  facing  the 
ends  of  spindles.  As  the  metal 
removed  by  the  parting  tool  is 
slight,  and  leaves  little  room  for 
the  knife  tool,  the  latter  is  there¬ 
fore  made  narrow  and  nearly 
pointed.  The  same  kind  of  tool 
is  also  much  used  in  turret  lathes 
for  turning  down  bars,  using  a 
very  deep  cut  and  a  fine  traverse 
feed.  Tools  having  their  cutting 
edges  corresponding  with  the 


J' 


B 


Fig.  65. 


contour  of  portions  of  the  work  are  made  to  requirements.  The 
commonest  are  the  convex  and  concave  shapes,  in  various  radii. 

Inside  tools  resemble  in  the  main  those  used  for  outside 
turning,  comprising  roughing,  which  can  be  fed  inwards  or  out- 


TOOLS  FOR  CUTTING  METAL. 


6i 

wards  for  roughing  (Fig.  65,  b),  or  for  finishing,  or  for  parting  off 
(c).  Besides  this,  there  are  the  internal  screw-threading  tools  for 
vee,  or  square  threads,  which  are  like  Fig.  65,  c, 
but  suitably  shaped  and  ground  at  the  cutting  end ; 
and  those  for  worms  of  the  sectional  form  in  Fig.  66, 
the  clearances  of  which  have  to  be  regulated  accord¬ 
ing  to  the  slope  of  the  thread  to  be  cut. 

The  question  of  the  best  forms  of  tools  to  use 
on  planing  and  shaping  machines  is  complicated  by 
the  conditions  under  which  the  tools  are  used. 

'I'hus  results  depend  on  overhang,  and  depth  of  cut 
nearly  or  quite  as  much  as  on  correct  formation.  The  typical 
roughing  tool  occurs  indifferently  in  all  forms,  very  much  cranked 
(Fig.  64),  or  scarcely  cranked  at  all  (Figs.  67  and  68).  The  first 
is  theoretically  correct,  the  second  incorrect,  yet  both  work  well 
under  suitable  conditions.  The  essential  difference  between  the 
two  is  this,  that  under  given  conditions  Fig.  64  will  not  dig  into 
the  work,  or  chatter,  and  Figs.  67  and  68  will. 

But  the  latter  are  used  more  extensively  than  the  former,  and  the 
reasons  for  this  seeming  contradiction  are  not  obscure.  In  the  first 
place,  solid  tools  are  made  of  steel  ranging  from,  say,  f  in.  square  to 
2  in.  square,  depending  on  the  nature  of  the  work  which  they  are 
designed  to  do,  and  they  are,  therefore,  very  rigid  under  ordinary 
conditions  of  duty.  Another  matter  is  that  the  machinist  invari¬ 
ably  endeavours  to  give  the  least  amount  of  overhang  possible  to 
the  tool,  by  bringing  the  tool-box  as  close  to  the  work  as  the  con¬ 
ditions  of  the  work  will  permit  of.  In  this  way  the  spring  of  the 
tool  is  reduced  to  a  practically  unappreciable  amount.  So  that 
in  Fig.  68,  if  the  edge  of  the  tool-box  is  brought  to  the  line  c — 
the  heaviest  cutting  can  be  performed  without  the  tool-point 
digging  into  the  work,  or  breaking  off.  c — d  would  be  possible  in 
the  majority  of  cases,  a — b  being  exceptionally  high  up. 

Figs.  67  and  68  represent  the  roughing  tools  commonly  used 
on  planer  and  shaper  for  cast  and  wrought  metals  respectively. 
The  differences  are  that  the  first  is  broader  at  the  cutting  point, 
and  that  the  cutting-angle  is  greater  than  that  in  the  second.  Ca.st 
metals,  being  more  crystalline,  do  not  offer  so  great  resistance  to 
the  tool  as  wrought  metals,  nor  is  so  much  heat  generated  during 
cutting.  So  that  broader  cuts  are,  as  a  rule,  practicable  with  the 
former  than  with  the  latter.  Experience  has  also  demonstrated 


62 


TOOLS. 


the  necessity  for  making  a  difference  in  the  cutting  angles  for 
cast  and  wrought  metals.  Usually  a  difference  of  about  io° 
is  made,  the  tools  for  wrought  metals  being  the  keener.  The  dif- 
erence  is  made  on  the  top  or  cutting  face,  there  being  no  necessity 
to  make  any  in  the  clearance  angle.  Often,  however,  though  not 
necessary,  there  is  such  a  difference  made,  the  clearance  angle 
being  slightly  greater  in  the  tools  for  wrought  than  in  those  for 
cast  metals.  Though  the  term  “  cast  metals,”  is  employed,  brass, 
and  gun-metal  are  excepted.  The  tool  commonly  used  for  these 
is  shown  in  Fig.  69.  There  is  no  front  rake,  and  the  clearance 
angle  is  in  practice  very  variable,  often  being  much  greater  than 
that  indicated.  The  resistance  to  cutting  is  so  slight,  that  a  large 
clearance  angle  is  possible  without  seriously  affecting  the  dura¬ 
bility  of  the  tool  point.  But  brass  and  gun-metal  are  very  com- 


Fig.  67. 


monly  planed,  and  shaped  with  the  same  tools  that  are  employed 
for  cast  iron  and  steel,  both  for  light  and  heavy  cutting.  If  the 
tools  are  stiff,  and  held  firmly,  there  is  no  perceptible  tendency 
to  “  draw  in,”  or  to  chatter  apparent. 

The  three  forms  illustrated  in  Figs.  67,  68,  and  69,  are  the 
types  upon  which  numerous  cutting  tools  used  in  planer  and 
shaper  are  based.  Each  of  these  is  of  the  straightforward  class — 
that  is,  it  is  usually  presented  perpendicularly,  or  normal  to  the 
surface  of  the  work,  and  the  traverse  feed  takes  place  at  right 
angles  with  the  tool  shank.  But  these  forms  of  tools,  and  methods 
of  presentation  by  no  means  cover  the  whole  range  of  work  which 
has  to  be  done.  Since  the  surfaces  which  have  to  be  machined 
in  planer  or  shaper  occur  in  many  positions,  they  necessitate 
correspondingly  varied  methods  of  presentation  of  the  tools.  It  is 
always  desirable  to  machine  the  whole,  or  as  large  a  portion  of 


TOOLS  FOR  CUTTING  I^LETAL. 


63 


a  job  at  one  setting  as  possible,  because  the  risk  of  error  due  to 
inaccurate  subsequent  setting  is  prevented.  The  swivel  tool¬ 
boxes  permit  of  a  great  deal  of  variation  in  methods  of  presenta¬ 
tion  of  tools.  But,  apart  from  this,  it  is  often  necessary  to  use 
tools  cranked  to  right,  or  left  hand,  and  both  roughing,  and 
finishing  tools  occur  in  these  forms.  The  reason  is  that  it  is 
frequently  not  possible  to  set  a  tool  at  an  angle  in  the  tool-box, 
as,  for  example,  when  it  has  to  pass  down  between  adjacent  ver¬ 
tical  parts  to  plane  some  portions  which  are  undercut,  or  which 
lie  at  an  angle.  The  following  figures  illustrate  the  principal 
forms,  shown  operating  on  surfaces  of  work  typical  of  those  for 
which  they  are  generally  best  adapted. 

In  Fig.  70,  A  and  b  illustrate  the  application  of  a  straight- 


Fig.  71. 


forward  tool  in  the  two  positions  in  which  it  can  be  used  most 
favourably,  a  is  the  position  suitable  for  horizontal  surfaces,  and 
this  is  how  the  bulk  of  planing  and  shaping  is  done,  b  represents 
it  as  on  vertical  surfaces.  But  the  method  of  presentation  shown 
at  B  is  only  possible  when  there  is  a  supplementary  tool-box  on 
one  of  the  vertical  sides  of  the  planing  machine,  or  on  a  supple¬ 
mentary  standard  by  the  side.  And  it  is  not  possible  at  all  to 
use  it  so  on  the  shaper,  so  that  many  vertical  faces  have  to  be 
planed  with  a  tool  set  diagonally,  as  at  c  or  d.  c  is  not  of  a  form 
quite  so  favourable  to  cutting  in  this  direction  as  d,  though  both 
are  employed  indiscriminately.  It  would  be  a  troublesome  job  to 
cut  down  an  angular  face  except  with  a  cranked  tool,  as  indicated 
at  E.  And  for  cutting  down  vertical  faces  in  confined  positions  in 
which  there  is  no  room  to  set  the  tools  at  an  angle,  as  in  Fig.  71, 


64 


TOOLS. 


the  use  of  cranked  tools  is  absolutely  necessary  to-the  production 
of  accurate  results.  The  straightforward  and  cranked  tools,  there¬ 
fore,  each  being  kept  in  forms  suitably  ground  for  cast,  and 
wrought  metals,  constitute  the  most  extensive  equipment  of 
planing  and  shaping  machines. 

The  tool  grooves  left  on  the  surface  of  the  work  are  always 
visible  as  distinct  grooves,  but  so  shallow  that  the  surface  is  suffi¬ 
ciently  accurate  for  very  many  purposes.  For  a  large  quantity  of 
work,  the  practice  is  to  take  two  cuts  with  the  same  roughing 
tool ;  the  first  with  a  deep  cut,  and  coarse  feed,  which  leaves  the 
surface  much  ridged  or  grooved,  and  the  second  with  a  shallow 
cut,  and  fine  feed,  which  reduces  the  work  to  the  finished  dimen¬ 
sions  required,  and  leaves  the  tool  marks  visible,  but  scarcely 
perceptible  to  the  touch  as  distinct  ridges.  For  the  finest 
work,  however,  this  is  neither  true  enough,  nor  is  it  finished 
sufficiently.  Then  the  broad-finishing,  or  broad-cutting,  tool  (Fig. 
72)  is  employed.  The  depth  of  cut  effected  with  this  is  almost 
imperceptible — a  mere  surface  cutting,  or  scraping  of  fine  shavings 
or  dust — but  the  traverse  feed  is  large.  From  a  |  in.  to  f  in.  is  a 
common  amount  of  traverse  for  average  work ;  but  on  large 
surfaces  |  in.  or  i  in.  is  often  given,  and  in  some  cases  even  this 
is  exceeded.  The  width  of  tool  is  greater  than  the  feed  imparted 
to  it,  say,  ^  in.  more  at  least,  and  the  extreme  corners  are  rubbed 
off  on  a  hone.  The  marks  of  these  tools  remain  visible  on  the 
surface  of  the  finished  work,  corresponding  in  width  with  amount 
of  feed  given.  It  is  to  remove  these,  and  to  impart  a  still  higher 
degree  of  accuracy,  that  scraping  is  resorted  to.  But  for  all 
except  the  highest  class  of  work  broad  finishing  is  practically 
true,  unless,  indeed,  the  machine  slides,  or  the  mode  of  setting 
the  work  produces  inaccuracy. 

These  are  the  typical  tools,  but  others  of  varied  forms  'are 
derived  from  them,  the  difference  being  in  outlines,  and  not  in 
cutting,  and  other  angles.  It  is  not  necessary  to  illustrate  all 
these,  since  tools  are  frequently  devised  for  special  jobs  of  work. 
Thus,  broad-cutting  tools  like  Fig.  72  are  commonly  made  right, 
and  left  handed  for  side  cutting,  or  cutting  at  angles,  similarly  to 
the  roughing  tools  in  Figs.  70,  71.  Tools  of  similar  type,  straight¬ 
forward,  are  used  for  cutting  or  finishing  grooves,  as  in  Fig.  73. 
Round-nosed  tools  of  various  radii  are  also  used  in  planer  and 
shaper ;  while  for  recesses,  cranked  tools  are  employed. 


TOOLS  FOR  CUTTING  METAL. 


65 


There  are  three  movements  of  planer  and  shaper  tools,  and 
each  has  various  rates,  depending  on  quality  of  metal,  condition, 
and  shape  of  the  tools  used,  and  the  nature  of  the  cutting  being 
done.  The  movements  are  the  travel,  or  forward  movement  of 
the  tool,  or  of  the  work ;  the  cutting  feed,  or  depth  to  which  the 
tool  penetrates  in  a  single  cutting  movement ;  and  the  traverse 
feed,  or  width  of  cut  taken  by  the  tool  during  a  single  cutting  or 
return  movement. 

The  rate  of  forward  movement  varies  from  about  15  ft.  to  40  ft. 
per  minute  respectively  in  the  case  of  the  hardest  materials,  and 
heavy  cuts ;  and  of  the  softer  materials,  and  lighter  cuts.  20  ft.  a 
minute  is  a  good  average  speed  for  cutting  cast  iron.  The  maxi¬ 
mum  speed  for  cutting  wrought  iron  with  a  single  tool  is  about  40 
ft.  per  minute  ;  a  very  usual  rate  is  30  ft.  But  so  much  depends 


on  feed,  depth  of  cut,  and  quality  of  metal,  that  those  are  simply 
averages.  Using  high  speed  steels  for  tools,  these  rates  are  easily 
trebled.  The  cutting  feed  or  depth  of  cut  varies  from  an  almost 
unappreciable  amount  up  to  f  in.  and  |  in.  deep.  The  traverse 
feed  or  width  of  cut  varies  from,  say,  in.  to  i  in.,  or  more,  in 
broad  cutting,  or  finishing  cuts. 

The  Armstrong  “gang”  planing  tool  (Figs.  74  and  75)  com¬ 
prises  a  holder  carrying  four  tools,  each  successive  tool  being  set 
laterally  a  little  in  advance  of  the  preceding  one.  Each  there¬ 
fore  cuts  deeper  than  its  predecessor,  and  the  result  is  that  a 
greater  aggregate  amount  of  cut  is  taken  than  would  be  possible 
with  a  single  tool  point.  The  advantage  of  this  is  very  apparent 
on  large  surfaces,  which  are  thus  planed  more  quickly  than  in  the 
ordinary  way.  The  holder  comprises  a  shank,  upon  which  the 

E 


66 


TOOLS. 


•  Ip 
*(<> 


Fig.  76. 


tool  head  is  fitted  with  a  projecting  stud.  Two  set  screws,  passing 
through  slots  in  the  head,  attach  it  firmly  to  the  shank,  while 
allowing  of  circular  swivelling  taking  place.  This 
latter  provides  the  means  for  setting  the  tools  in 
successively  deeper,  the  swivel  of  the  holder  being 
graduated,  so  that  an  exact  and  known  amount 
of  swivel  can  be  imparted.  This  slewing  naturally 
alters  the  side  clearance  of  the  tools  somewhat,  but 
the  amount  is  insufficient  to  be  noticeable.  The 
diagram.  Fig.  76,  shows  the  effect  of  this,  the  left 
hand  side  cutting  -deeply,  and  so  having  less 
clearance  than  the  one  on  the  right,  which  is 
cutting  finely  and  therefore  has  not  been  swivelled 
so  much  in  the  holder.  The  arrow  shows  the 
direction  of  motion  of  the  planer  table. 

In  the  slotting  machine,  no  feed  whatever  can  be  given  to  the 
tool.  In  this  respect  it  differs  from  both  planer  and  shaper.  All 
feeds  are  imparted  to  the  table  on  which  the  work  is  bolted. 
Heavy  feeds  can  be  utilised,  because  the  cutting  force  passes 
mainly  through  the  longitudinal  axis  of  the  tool,  which  is  in  line 
with  the  ram,  and  the  latter  is  always  massive,  and  moves  in  long 
slides.  The  tool  always  tends  to  spring  backwards  under  the 
stress  of  cutting ;  but  this  is  diminished  by  using  a  stiff  shank, 
and  reducing  the  amount  of  its  projection  to  a  minimum  for  each 
job.  To  permit  of  this,  the  height  of  the  ram  above  the  table  is 
rendered  adjustable.  For  some  work,  a  tool  like  a  planer  tool  is 
used,  and  set  at  right  angles  with  the  axis  of  the  ram  (Fig.  78) ; 
but  it  is  mostly  employed  when  the  ordinary  straightforward  type 
is  not  suitable.  An  objection  to  the  usual  form  of  tool  is  that  it 
cannot  be  lifted  clear  of  the  work  during  the  up,  or  non-cutting 
stroke.  Arrangements  for  lifting  the  tool  have  been  devised,  but 
are  not  to  be  seen  on  one  out  of  a  hundred  machines.  In 
practice,  the  friction  during  the  up  stroke  is  not  very  detrimental, 
because  the  cutting-edge  is  not  ground  acutely,  and  does  not 
soon  suffer.  Neither  have  tool-holders  met  with  much  favour 
in  slotting  machines,  notwithstanding  that  there  are  one  or  two 
good  ones  offered  for  sale. 

A  few  useful  solid  slotting  tools  are  grouped  together  in  Figs. 
77  and  78.  In  the  first  three  figures  the  tool  is  shown  in  side 
elevation,  and  in  inverted  plan — that  is,  the  bottom  figures  repre- 


TOOLS  FOR  CUTTING  METAL. 


67 


sent  the  cutting  edges  looked  at  from  below.  In  each  instance 
the  cutting  point  or  edge  is  to  the  left  hand.  In  Fig.  77  the  first 
tool  to  the  left  is  of  the  diamond 
point  type,  and  is  used  both  for 
fine  cutting,  and  for  finishing  right 
into  the  corners  of  angular  work. 

The  second  and  third  are  round¬ 
nosed  tools,  used  for  roughing  out, 
and  also  for  finishing  concave 
work.  The  fourth,  seen  in  side 
and  front  views,  is  a  common  tool, 
used  both  for  roughing,  and  finish¬ 
ing,  and  generally  for  completing 
work  at  one  cut,  and  specially  for 
key-way  grooving,  being  tapered 
backwards  from  the  cutting  edge. 

Although  the  essential  forms 
of  the  tools  used  on  slotting 
machines  are  not  numerous,  yet  each  occurs  in  so  many  dimen¬ 
sions,  that  the  total  numbers  run  up  rapidly.  There  may  very 
well  be  15  or  16  key-waying  tools  at  a  machine,  all  of  precisely 
the  same  form,  but  of  different  widths.  And  so  of  other  tools. 
Hence  the  equipment  of  an  ordinary  slotting  machine  will  run  up 
to  70,  80,  or  100  separate  tools.  There  are  two  ways  in  which 
the  amount  of  metal  in  slotting  tools  is  reduced.  One  is  by 
making  the  tools  double-ended — a  very  common  practice — as  in 
the  key-grooving  tool  to  the  right  of  Fig.  77.  The  other  is  by 
using  several  detachable  tool  points  in  one  shank,  as  seen  in  side 
and  front  views  to  the  left  of  Fig.  78.  The  latter  has  other 
advantages  besides  the  economy  of  metal ;  it  often  saves  time — 
the  time  occupied  in  changing  and  setting  the  solid  tools.  It  also 
furnishes  the  lighter  tools  with  a  substantial  shank,  by  which  they 
are  enabled  to  operate  more  steadily  and  sweetly  than  if  forged 
on  a  solid  shank  of  light  proportions.  In  one  example  the  tool 
point  is  held  with  one,  or  with  both  of  the  set  screv^'s  shown ;  in 
the  other  a  wedge  only  is  used. 

Two  tools  are  often  used  at  one  time  for  cutting  either  on 
external  or  internal  surfaces,  an  example  being  a  horn  block  for 
a  locomotive,  which  is  machined  for  the  vertical  movements  of 
the  axle-boxes.  A  single  block  only,  or  two  or  more,  are  often 


68 


TOOLS. 


superimposed  and  machined  at  once.  The  tools  are  not  only 
clamped,  but  a  stretcher  of  hard  wood  is  inserted  to  keep  them 
from  being  sprung  inwards  through  the  stress  of  cutting.  The 
reason  is  that  the  manner  in  which  the  tools  are  set  deprives  them 
of  the  support  of  the  face  of  the  ram  during  cutting,  and  the 
pinching  of  the  clips  might  not  be  sufficient  to  prevent  springing 
or  working  back  of  the  tools.  There  are  many  jobs  where  the 
inner  faces  which  have  to  be  slotted  are  situated  too  closely  to¬ 


gether  to  permit  of  the  convenient  employment  of  two  separate 
tools.  To  avoid  the  waste  of  time  involved  in  the  use  of  a  single 
tool  operating  in  succession  on  the  two  faces,  one  formed  like  that 
to  the  right  of  Fig.  78  in  front  and  edge  views  is  used,  when  the 
number  of  pieces  to  be  slotted  will  permit  of  the  cost  of  making 
such  a  special  tool.  The  width  of  the  tool  is  precisely  the  same 
as  the  finished  width  between  the  faces  of  the  bosses,  and  there 
is  but  one  cut  taken  over  them.  The  hollow  is  simply  imparted 
for  facility  of  grinding  the  cutting  faces. 


CHAPTER  VI. 


The  Shearing  Action,  and  Shearing  Tools. 

Shearing,  a  detailed  operation — Diagonal  Cutting  with  Chisel — Fox  Trimmer 
— Square  and  Skew  mouthed  Rebate  Plane — Turning  Chisel — Reamers 
and  Milling  Cutters — Roughing  Tools — Walker  Planer  Tool — Profiled 
Tools — Shear  Blades — Necessity  for  Support  to  the  substance  being 
Shorn — Staggered  Cutting  in  Mills — Flat  Drill — Combination  of  Shearing 
with  Staggering. 

The  labour  involved  in  cutting  hard  materials  is  so  great 
that  various  devices  are  adopted  in  order  to  lessen  it  as 
far  as  practicable.  One  of  these  is  to  remove  the  shavings 
or  chips  by  a  detailed  action  — a  successive,  but  unbroken  method 
of  cutting,  which  is  termed  shearing ;  the  other  is  similar  in  its 
results,  though  different  in  its  operation,  and  embodies  an  action 
that  breaks  up  the  continuity  of  the  chips.  In  a  few  instances 
the  two  devices  are  combined — namely,  the  shearing,  and  the 
staggering  cut. 

The  first  is  applied  in  the  case  of  tools  operated  both  by  hand, 
and  by  machine,  on  timber,  and  on  metal.  When  great  resist¬ 
ance  is  offered  to  cutting  with  a  chisel,  the  hand  instinctively 
slides  it  along  diagonally,  and  so  applies  the  muscular  effort  to 
greater  advantage.  It  comes  more  naturally  on  hard,  than  on 
soft  wood,  for  it  is  nearly  impossible  to  take  a  fair  cut  across  the 
end  grain  of  the  hard  woods,  if  a  chisel  is  actuated  straightforward. 
The  labour  of  planing  straightforward  over  a  considerable  width 
is  great,  being  evident  in  the  work  of  a  coarsely  set  trying  plane. 
As  an  extreme  case  take  the  power  planing  machines.  A  common 
panel  planer,  having  parallel  knives,  say  24  in.  in  length,  will 
absorb  something  like  3  H.P.,  and  then  will  pull  up  its  engine  if 
forced  to  take  exceptionally  deep  cuts. 

One  of  the  most  useful  of  the  modern  tools  in  the  pattern 
shop,  and  joinery  is  the  Fox  trimmer,  and  its  great  value  lies  in 


70 


TOOLS. 


the  nature  of  its  shearing  cutting.  The  blades  a  a,  Fig.  79,  are 
screwed  to  their  backing  at  an  angle  of  45°.  Being  actuated  by  a 
long  lever,  pinion,  and  rack,  they  are  slid  longitudinally  for  right, 
and  left  handed  cutting.  The  work  rests  on  the  table  b,  and 
adjustable  wings  at  the  ends  permit  of  setting  the  work  either 
square  across,  or  to  any  angle.  The  trimmer  shears  off  thick  or 
thin  chips  at  one  traverse  across  the  entire  area  of  an  end  pre¬ 
sented  to  it,  and  wkh  perfect  truth,  and  as  clean  as  though  planed, 
due  mainly  to  the  shearing  action  of  the  blades. 

Since  the  shearing  cut  produces  a  clean  surface,  that  affords 
another  reason  why  it  is  sometimes  adopted  in  preference  to  the 
straightforward  cut.  The  difference  is  very  marked — for  example, 
in  a  square-mouthed  rebate  plane  working  across  coarse  grain  in 
soft  wood,  and  a  skew-mouthed  one.  The  latter  not  only  operates 
with  less  labour,  but  it  cuts  much  more  sweetly,  taking  off  curling 


shavings,  and  leaving  a  sleek,  polished  surface.  Or  plane  a  rebate 
lengthwise  with  the  two  types  of  planes ;  and  not  only  will  the 
labour  required  in  the  first  be  bound  to  be  greater,  but  the  surface 
which  is  cut  will  not  be  left  so  smooth,  for  a  slight  chatter  will  be 
found  to  have  left  its  marks  in  places. 

Examples  of  this  kind  might  be  multiplied,  but  one  more 
may  suffice — the  turning  chisel.  The  action  here  is  always  that 
of  shearing ;  the  scraping  chisels  are  not  in  the  running  for  re¬ 
moving  material  rapidly,  or  for  leaving  clean,  smooth  surfaces. 

The  difference  which  we  note  in  the  rebate  planes,  and  in 
turning  and  scraping  chisels  is  perfectly  paralleled  in  the  edge 
types  of  reamers  and  milling  cutters.  Few  of  these  of  over  an 
inch  in  width  have  their  teeth  set  parallel  with  the  axis,  but  they 
are  placed  at  an  angle  therewith  (see  Fig.  117,  p.  99),  to  take  a 
series  of  shearing  cuts,  'fhe  tendency  to  chatter  is  thus  lessened, 


SHEARING  TOOLS. 


71 


and  the  cut  surface  is  left  smooth.  It  is  partly  due  to  their  shear¬ 
ing  action  that  these  cutters,  with  little  or  no  top  rake,  act  so 
efficiently.  Latterly  the  tendency  has  been  to  increase  this  in 
amount,  until  on  mills  of  considerable  length  the  spiral  twist 
becomes  very  marked.  In  some  few  mills  the  angle  is  found  to 
measure  as  much  as  50°  with  the  axis  of  the  cutter.  Fig.  118,  on 
p.  99,  illustrates  a  French  cutter,  and  some  of  the  Pratt  &  Whitney 
mills  have  angles  as  great.  Again,  in  built-up  mills  each  separate 
piece  is  often  set  with  its  teeth  in  the  opposite  direction  to  that 
one  adjacent  (Fig.  119,  p.  99).  Each  shears,  but  the  endlong 
stress  of  one  is  counteracted  by  that  of  the  other.  By  such 
devices  work  of  from  24  in.  to  30  in.  in  width  is  tooled  readily. 

When  the  action  of  most  metal-cutting  tools  is  considered, 
few  are  found  in  which  the  action  of  the  shearing  cut  does  not 
occur,  and  this,  without  regarding  those  which  are  commonly  known 
as  shearing  tools.  Even  the  common  roughing  tools  act  partly 
by  shearing,  since  sloping  sides  and  edges  take  a  share  in  cutting. 
The  entire  absence  of  such  an  action  in  parting-off  tools,  and  in 
broad  finishing  tools,  whether  straight,  or  curved  in  profile,  ex¬ 
plains  why  they  are  so  hard  to  operate,  and  so  liable  to  chatter. 
A  familiar  example  of  the  shearing  cut  occurs  in  the  knife  tools 
used  for  facing  ends.  These  are  often 
bevelled  so  that  the  edges  slope.  The 
same  formation  is  adopted  in  some 
roughing  tools  of  the  knife  class  used 
in  turret  lathes. 

The  Walker  planer  tool  shown  in 
Fig.  80,  is  designed  for  taking  broad 
finishing  cuts.  Its  value  lies  in  its 
shearing  action,  which  not  only  renders 
the  cutting  easy,  but  prevents  the 
breaking  out  of  the  metal  at  the  edges  of  iron  castings.  The 
angle  of  the  slope — namely  60° — is  seen  in  plan. 

Amongst  the  most  remarkable  tools  of  recent  years  are  those 
of  the  forming  type,  used  for  brass  finishers’  work.  Whatever  the 
shape  of  a  brass  casting,  provided  it  admits  of  turning  a  profile,  a 
tool  can  be  made  to  the  profile,  and  slid  tangentially  thereto,  cut¬ 
ting  and  finishing  over  the  whole  breadth  at  one  traverse,  and  pro¬ 
ducing  any  number  of  pieces  all  exactly  alike.  One  of  these  tools 
is  shown  in  Fig.  81,  with  the  piece  of  work  it  is  designed  to  finish 


72 


TOOLS. 


beneath.  The  tools  are  milled  to  the  section  required,  and  never 
lose  their  form,  because  they  are  ground  at  the  end  only.  The 

end  is  bevelled  to  an  angle  of  30°,  and 
it  is  remarkable  how  very  sweetly  the 
cutting  action  is  performed,  as  the 
cutter  goes  gradually  through  its  work. 
There  is  no  limit  to  the  sectional 
shapes  that  can  be  formed  in  this  way, 
and  one  movement  of  a  lever  is  all  that 
the  attendant  has  to  give  to  operate 
the  tool. 

The  shearing  cut,  therefore,  is  a 
power  in  the  rapid  removal  of  metal, 
just  as  it  is  in  the  side  chisel  for  wood, 
and  in  the  diagonal  movement  of  the 
common  chisel,  instinctively  imparted 
when  paring  the  end  of  a  piece  of 
timber.  Just  as  it  is  also  in  the  skew¬ 
mouthed  rebate  plane,  and  in  the  little 
spill  plane,  which  shears  off  the  curling 
shavings  that  wrap  tightly  round  it  into 
a  conical  spill,  with  which  to  light 
your  pipe. 

Without  the  diagonal  cut,  the  ma¬ 
jority  of  the  shearing  tools  would  be 
nearly  inoperative.  Only  by  their 
gradual  action  (see  the  diagram,  Fig. 
82,  which  represents  the  angles  of  a 
pair  of  shear-blades)  can  they  be  made 
to  sever  materials.  It  would  be  clearly 
impossible  with  any  amount  of  power 
to  close,  .say,  the  4  ft.  blade  of  a 
shearing-macbine  instantly  on  a  thick  plate  without  damaging  the 
blade,  and  plate.  The  question  of  tool  angles  here  seems  to  be 
of  much  less  importance 
than  that  of  the  thickness 


Fig.  82. 


of  plate  shorn,  and  of  the 
degree  of  support  afforded 
to  it.  There  is  no  parallel  between  the  removal  of  a  shaving  of 
metal  with  a  cutting  tool,  and  the  separation 'of  a  mass  of  metal 


SHEA/^/NG  TOOLS. 


73 


through  a  considerable  thickness.  A  shaving  is  curled  off  or 
broken  immediately  it  is  severed,  but  a  plate  in  course  of  severance 
is  backed  up  and  rigidly  supported  by  the  mass  of  metal  behind. 
Hence  the  action  of  the  tool  is  only  slightly  cutting,  and  more 
largely  squeezing — detrusive,  a  violent  forcing  of  the  material 
apart — and  in  a  plane  parallel  with  the  faces  of  the  shears. 

The  diagonal  severance  occurs  in  the  common  scissors,  and 
garden  shears,  sheep  shears,  and  allied  tools,  though  in  a  much 
reduced  degree.  The  humble  lawn  mower  is  fitted  with  shear 
blades.  The  diagonal  punch.  Fig.  230,  p.  160,  embodies  the 
same  principle. 

It  is  essential  to  the  successful  opera¬ 
tion  of  all  the  shearing  class  of  tools  that 
the  work  be  properly  supported  between 
the  blades,  or  between  the  edge,  and  a 
bolster.  If  there  is  an  open  space  between 
which  the  work  can  become  squeezed,  it 
will  be  bent,  and  distorted  (see  Fig.  83,  a). 

What  is  seen  to  happen  in  loosely-jointed 
scissors  would  also  occur  in  engineers’ 
shears  if  the  blades  were  not  in  opposition 
in  the  plane  of  cutting  (Fig.  83,  b).  But 
instead  of  the  metal  getting 'squeezed  be¬ 
tween,  it  would  be  bent  somewhat  at  the 
severed  edges  and  distorted,  and  the  work 
of  the  shears  would  be  interfered  with, 
and  increased  by  reason  of  the  want  of 
adequate  support,  and  would  probably 
become  blocked  and  injured. 

The  staggering  of  teeth  is  variously  done.  Fig.  154,  p.  117, 
illustrates  a  common  practice.  Mills  are  built  up  thus  on  the 
hit-and-miss  style,  so  that  the  teeth  shall  come  into  action  in  quick 
succession,  instead  of  continuously,  along  a  considerable  length. 
The  penetrative  power  is  increased,  and  wide  profile  work  is 
tooled  with  comparative  ease. 

Fig.  199,  p.  143,  is  another  illustration  of  staggering,  seen  in 
the  flat  drill  used  in  screw-machines  for  roughing-out  a  tapered 
hole  rapidly.  This  is  followed  by  the  smooth  tapered  reamer  in 
Fig.  200,  p.  143. 

The  last  advance  to  be  noted  is  the  combined  shearing  and 


Fig.  83. 


74 


TOOLS. 


staggering  of  cutting  edges,  by  which  their  penetrative  power  is 
still  further  increased,  and  in  this  way  wide  work  is  milled  with 
increase  in  depth  of  cut.  Either  the  mill  is  formed  in  the  usual 
way  by  cutting  the  spirals  on  a  universal  machine,  and  the  length 
of  a  spiral  is  broken  up  into  short  teeth  subsequently,  or  the 
separate  teeth  are  inserted  into  the  body  of  the  mill  in  diagonal 
lines.  In  each  the  effect  is  practically  the  same.  In  some  cases 
the  mill  is  made  hollow,  so  that  the  teeth  shall  be  flooded  with 
lubricant  during  cutting. 


SECTION  11. 


SCRAPING  TOOLS. 

CHAPTER  VII. 

Examples  of  Scraping  Tools. 

The  Nature  of  the  Operation — The  Metal  Worker’s  Scrape — Some  Wood- 
Turner’s  Finishing  Tools — Arboring  Tools — Fly  Cutters. 

SCRAPING  tools  form  a  large  group,  and  they  are  also  of 
much  importance,  because  many  tools  occur  on  the  border 
line,  where  it  is  often  difficult  to  classify  them  either  as 
cutting  or  scraping. 

Scraping  is  an  operation  which  is  not  incisive,  that  is,  the 
wedge  formation  of  the  tool  is  absent,  and  therefore  practically  it 
has  no  penetrative  power,  and  cannot  remove  either  shavings,  or 
chips. 

A  scraping  tool  used  in  lathe,  or  planer  is  usually  held  and 
operated  with  its  axis  normally  to  the  surface  of  the  work.  But 
a  hand  scrape  is  generally  held  at  an  angle  therewith. 

Scrapes  are  used  only  as  corrective  tools  for  fine  processes, 
since  they  cannot  remove  material  in  quantity,  but  only  in  the 
form  of  dust,  or  minute  particles.  But  their  great  value  lies 
mainly  in  the  minute  precision  of  results  attainable  by  their  use, 
and  in  a  lesser  degree  in  the  fact  that  they  can  be  used  on  very 
hard  material,  which  incisive  tools  will  not  touch. 

The  scraping  tools  include  the  following : — 

Those  used  by  metal-workers,  in  lathe,  planer,  and  other 
machine  tools  ;  those  employed  by  wood-turners,  the  toothing 
plane  of  the  cabinetmaker,  for  preparing  veneering  surfaces  for 
gluing,  the  scrape  made  of  a  bit  of  broken  saw  blade  for  smoothing 
planed  surfaces,  preparatory  to  glasspapering,  the  scrape  of  the 


76 


TOOLS. 


metal-worker,  employed  either  as  a  corrective  tool,  or  for  fine 
frosting. 

The  common  scrape  of  the  metal-worker  is  shown  in  its  more 
usual  form  in  Fig.  84.  It  is  pushed  forward  in  short  strokes, 

while  held  at  a  low  angle 
with  the  face  of  the  work. 
The  cabinetmaker’s  scrape 
Fig.  84.  is  held  a  few  degrees  over 

from  the  perpendicular. 

Figs.  85  illustrate  tools  used  by  wood-turners,  which  act  purely 
by  scraping.  They  are  the  round  nose  a,  the  right,  and  left  hand 


fl 


Fig.  85. 


c 


side  tools  b,  and  the  diamond  point  c,  which  is  a  union  of  the  two 
forms  B.  The  firmer  chisel  is  also  used  as  a  scrape  by  the  wood- 


n 

b 

■ 

1 

Fig.  86. 


fi 


turner.  The  metal-turner  employs  scrapes  in  the  form  of  finishing 
tools  for  all  metals  and  alloys,  including  straight-edged  tools,  and 


SCRAPING  TOOLS. 


77 


B 


those  with  convex  and  concave  edges,  parting  tools,  and  others 
(see  Chap,  V.).  Many  facing  tools  are  purely  scrapes. 

Figs.  86  illustrate  facing  tools  which  act 
by  scraping  only.  Fig.  86,  a,  is  used  for 
cutting  faces  on  the  inner  side  of  cylinder 
covers,  &c.,  to  receive  the  bolts.  The  cutter 
a  is  wedged  in  the  arbor  d,  which  just  fits 
the  drilled  bolt  hole.  In  Fig.  86,  b,  a  cutter 
is  shown  operating  in  turn  on  inside  faces  of 
bosses.  Fig.  87  is  a  hand  facing  arbor,  in 
which  the  cutter  a  is  fed  to  its  work  by 
tightening  the  nut  b.  It  is  rotated  by  a 
wrench  on  the  square  neck  c.  Other  ex¬ 
amples  of  facing  cutters  are  given  in  Chap. 

XII.,  p.  127. 

Another  type  of  scraping  tool  is  the  fly 
cutter  (Fig.  88),  used  to  a  moderate  ex¬ 
tent  in  some  light  operations,  notably  that 
of  cutting  wheel  teeth  of  small 


r?.ii 


L 

J 

Fig.  87. 


dimensions,  and  the  teeth  of  mortise  wheels.  Its  advan¬ 
tage  lies  in  the  ease  with  which  profiles  can  be  produced 
without  the  trouble  and  expense  of  making  a  complete 
circular  cutter. 

It  is  necessary  to  distinguish  between  the  scrape, 
and  the  cutting  tool,  otherwise  one  is  apt  sometimes 
to  confound  the  two.  These,  with  the  shearing  action, 
are  often  all  represented  in  the  groups  of  tools  to  be  noticed 
in  subsequent  chapters. 


Fig.  88. 


SECTION  III. 


TOOLS  RELATED  TO  BOTH  CHISELS  AND 

SCRAPES. 

CHAPTER  VIII. 

Saws. 

* 

Wide  Scope  of  the  Subject— Saw  Teeth,  Scrapes  and  Chisels — Shapes  varied 
to  suit  Materials — Examples  —Spacing — -Types  of  Saws — Reciprocating — 
Continuous — Variations  in  Speeds — Tension  of  Blades — Thickness  of 
Blades — Stiffening  of  Blades — Back  Saws — Wear  of  Teeth — Degree  of 
Set — Keeping  Saws  in  Order — Set — Its  Amount  and  Regularity — Methods 
of  Setting — by  Bending — by  Hammering — Test  of — Sharpening  Saws — 
Topping  the  Teeth — by  Stoning — by  Filing — Files  for  sharpening — 
Angles  for  Filing— Gulleting — The  Use  of  Saws — Forcing — -Buckle  — 
Packing — The  Place  of  Coarse  and  Fine  Teeth — Plolding  Work — Cutting 
to  a  Line. 

points  to  be  considered  in  the  economical  working  of 
I  saws  would  never  be  remotely  realised,  apart  from  a 
considerable  experience  in  their  use.  Are  they  scrapes, 
or  chisels?  What  is  the  reason  of  the  vast  differences  which 
exist  in  the  shapes  of  their  teeth,  in  their  spacing,  and  their 
degree  of  set?  Neither  of  these  admit  of  a  reply  which  would 
not  be  open  to  some  criticism.  And  the  devices  for  keeping 
these  teeth  in  order,  and  maintaining  them  in  full  efficiency, 
admit  of  much  discussion  and  differences  of  opinion. 

It  will  assist  us  in  understanding  the  action  of  saws  if  we  con¬ 
sider  each  tooth  as  a  distinct  tool.  It  will  then  be  apparent  that 
the  teeth  of  all  saws,  except  cross-cuts  and  those  used  for  metal,  are 
chisels,  and  mostly,  too,  with  shearing  action  included.  The  cross¬ 
cut  tears  the  fibres,  the  ripping  does  not,  but  each  tooth  severs  a 
minute  particle  of  the  wood.  The  cross-cut  operates  in  both  direc¬ 
tions,  the  ripping  saws  in  one  direction  only.  The  hardness,  soft- 


SAWS. 


79 


ness,  or  stringiness  of  the  ^tood  also  govern  the  forms  of  teeth,  apart 
from  that  of  their  scraping,  or  cutting  action.  Thus,  the  shapes 
of  saw  teeth  used  for  ripping,  rake  in  various  degrees,  a  selection 
of  which  is  given  in  Figs.  89,  107,  108,  those  having  the  more 
obtuse  angles  being  used 
for  hard,  and  stringy,  and 
knotty  stuff,  and  those 
with  acute  angles  for  soft, 
clean  materials.  On  these 
leading  forms  the  changes 
are  rung  in  various  de¬ 
grees,  in  various  shades  of 
difference. 

A  rip,  or  half-rip  saw 
is  the  proper  tool  for 
cutting  down  thick  plank¬ 
ing  of  soft  wood  wiVA  the 
grain,  and  it  has  the  least 
amount  of  set  of  any  saw, 
proportional  to  its  size,  of  course.  But  a  saw  having  smaller 
teeth,  called  distinctively  a  “hand-saw”  (Fig.  90),  is  that  in  com¬ 
monest  use,  and  is  generally  used  as  a  “cross-cut,”  that  is,  for 
cutting  planks,  and  boards  across  the  fibres,  and  then  it  contains 
the  greatest  amount  of  set,  and  most  of  all  for  soft,  wet  woods. 
Fig.  89,  A,  shows  the  teeth  of  a  rip  saw  to  full  size ;  Fig.  89,  b, 
that  of  a  half-rip ;  and  c  that  of  a  hand-saw  for  cross-cutting. 


N^v/^/s/sAv/VVNv/\A  C 

Fig.  89. 


Below,  at  d  and  e,  are  shown  the  teeth  of  a  tenon,  and  a  dovetail 
saw.  A  rip  contains  about  two  and  a  half  teeth  to  the  inch,  a 
half-rip  three  and  a  half,  a  hand-saw  four  and  a  half  to  five  and  a 
half,  a  panel  saw  seven  or  more,  a  tenon  saw  ten,  a  dovetail  saw 
sixteen  to  twenty. 

The  degrees  of  coarseness  and  fineness  in  saws  are  also 
expressed  in  “  points.”  The  number  of  “  points  ”  is  one  more 


8o 


TOOLS. 


than  the  number  of  teeth  in  the  inch ;  an  8  point  saw  has  but 
seven  teeth.  This  is  the  American  style. 

The  type  of  tooth  shown  in  Fig.  89,  but  with  either  more  or 
less  hook,  and  triangular,  or  gulleted,  is  universal  in  all  saws  that 
have  to  cut  in  one  direction,  such  as  ripping,  hand,  panel,  tenon, 
dovetail,  band,  and  circular.  But  when  a  saw  has  to  cut 
alternately  in  two  directions,  as  the  cross-cut,  the  teeth  are 
formed  differently.  The  common  hand-saw,  set  especially  for 


cross-cutting,  is  an  exception.  Cross-cut  saws  are  generally  two- 
handled,  so  that  two  men  can  operate  them ;  short  ones,  however, 
are  made  one-handled,  and  as  they  cut  in  both  directions,  equal 
pressure  is  exercised  both  ways,  whereas  with  a  hand,  or  tenon 
saw  the  workman  instinctively  relieves  the  weight  of  the  saw  from 
the  cut  on  the  back  stroke,  and  bears  harder  on  the  forward  or 
cutting  one. 

It  follows ^that  a  saw  cutting  both  ways  must  be  a  compromise 
in  respect  to  the  shape  and  method  of  action  of  the  teeth. 


In  a  cross-cut  saw  the  typical  teeth  are  shaped  as  equilateral 
triangles,  with  the  slopes  equal  on  both  sides  (Fig.  91).  That 
is  how  most  English  cross-cuts  have  been  made  for  generations. 
But  these  are  open  to  two  objections :  first  that  the  retreating 
faces  of  the  teeth  are  not  favourable  to  good  cutting  action — the 
rake  of  the  teeth  being  30°  back  from  the  perpendicular,  and 
second  that  there  is  little  room  for  the  sawdust  to  get  clear  of 
the  teeth.  Both  faults  are  much  more  objectionable  in  soft 


SA  WS. 


8i 


stringy  woods  than  in  hard  powdery  stuff.  The  M  teeth  (Fig. 
92),  in  their  various  modifications,  are  designed  to  obviate  these 
evils.  This  is  an  old  form  that  fell  into  disuse  in  England,  was 
revived  in  America,  and  is  now  sold  extensively  here.  It  is 
modified  in  several  ways, 
both  in  the  shapes  of  the 
M  teeth,  and  in  their  alter¬ 
nation  with  teeth  of  other 
forms. 

Gulleting  (Fig.  93)  is  an 
important  feature  in  the 
teeth  of  saws  working  regu¬ 
larly  in  soft  woods,  as  giving  more  clearance  to  the  dust.  It  is 
especially  applied  to  circular  saws,  which  are  most  rapid  in  action, 
and  to  pit  saws.  Gulleting  is  much  more  important  in  saws 
running  at  high  speeds  than  in  other  types.  Hence  circular  saws 
generally  have  their  teeth  thus,  and  the  larger  the  saw,  and  coarser 
the  teeth,  the  deeper  is  the  gulleting. 

The  spacing  of  saw  teeth  is  a  matter  of  more  importance  than 


Fig.  94. 


Fig.  95- 


it  might  seem  to  be  on  first  thoughts.  The  case  is  one  that  has 
its  parallel  in  the  pitch  of  milling  cutters.  These  were  formerly 
pitched  too  finely,  which  caused  the  cuttings  to  choke,  just  as 
wood  dust  will  choke  the  teeth  of  a  saw  having  small  spacings. 
But  there  is  no  universal  rule  for  this,  since  some  woods  choke 
more  quickly  than  others.  Yellow  pine,  for  instance,  will  work 
better  with  more  spacing  than  stringy  spruce  will  require. 

There  are  four  broad  types 
of  saws — the  reciprocating,  the 
Fig,  g6.  circular,  the  band,  and  the  cylin¬ 

drical.  The  latter  is  restricted 
to  surgical  operations  on  the  cranium. 

The  reciprocating  saws  include  all  hand  (Fig.  90),  back 
(Fig.  94),  and  turning,  or  sweep-cutting  saws  (Figs.  95  and  96), 
including  the  bow  saws,  the  frame  or  gang  saws,  the  fret  saws,  or 

F 


82 


TOOLS. 


jiggers,  used  for  sweep-cutting,  the  hack  saws,  pit  saws,  and  the 
cross-cuts.  The  circulars  include  but  one  class,  though  varied 
immensely  in  size,  forms  of  teeth,  precise  functions,  and  arrange¬ 
ments,  and  including  those  both  for  operating  on  metal,  and  wood. 
The  band  or  ribbon  saws  are  continuous  in  action,  like  the 
circulars,  and  like  those,  are  used  for  metal  and  timber.  They 
are  made  in  widths  ranging  from  about  ^  in.  to  6  in.,  or  8  in. 

In  all  the  reciprocating  saws  except  the  cross-cuts,  the  back 
stroke  is  lost,  as  is  that  of  the  metal  planer,  shaper,  and  slotter 
among  machine  tools.  But  in  the  circular  and  band  saws  the 
cutting  proceeds  uninterruptedly,  as  does  that  of  the  lathe,  the 
milling  cutter,  and  the  grinding-wheel. 

As  too  there  are  certain  speeds  in  lathe,  milling  machine,  and 
grinder,  which,  though  varying  with  the  materials  cut,  are  nearly 
constant  for  the  same  kinds,  so  there  are  certain  best  speeds  for 
continuously  cutting  saws.  Saws  are  not  run  at  the  same  speeds 
for  all  woods,  any  more  than  lathe  tools,  milling  cutters,  and 
grinding  wheels  are.  They  can  be  run  too  slowly,  or  too  fast;  in 
either  case  the  teeth  get  dull.  In  the  first  instance  they  lose  their 
edges  by  mere  friction,  in  the  second  by  friction  also;  but  in 
both  cases  the  point  is  that  the  proper  amount  of  dust  is  not 
removed  in  proportion  to  the  speed  of  the  saws,  and  the  wear 
upon  the  teeth.  There  is  waste  involved  in  one  case  as  there  is 
in  the  other.  An  experienced  saw  hand  will  avoid  both,  by 
ascertaining  the  best  rates,  meaning  the  most  efficient  ones,  for 
different  materials,  after  which  the  thing  is  to  feed  regularly. 
The  metal-cutting  saws  operate  at  a  high  speed  in  the  thin- 
bladed  “hot  iron  saws,”  and  very  slowly  in  the  thick-bladed 
“cold  iron  saws.” 

Other  important  differences  in  saws  are  those  which  arise  from 
their  tension,  from  the  amount  of  support  afforded  to  their  blades, 
and  from  the  direction  in  which  they  are  operated. 

If  a  saw  is  thrust  to  its  work,  and  nothing  but  the  natural 
rigidity  of  the  plate  is  utilised,  then  the  latter  cannot  be  so  thin 
as  when  the  opposite  conditions  exist.  But  a  thin  plate  is 
always  more  economical  than  a  thick  one,  because  it  causes  less 
waste  in  dust,  and  this  is  a  very  important  point  where  large 
quantities  of  material  are  being  converted,  as  in  sawmills.  A 
thin  blade  also  takes  less  power  to  operate  it,  hence  one  reason 
of  the  workman’s  preference  for  a  thin  hand-saw. 


SAWS. 


83 


Thin  blades  are  stiffened  in  various  ways,  in  different  kinds 
of  saws.  One  is  to  strain  them  tightly,  as  in  frame,  or  gang 
saws,  in  which  case  the  tendency  to  bend  under  thrust  is  taken 
up  by  the  tension  of  the  blades.  In  the  band  saws,  rigidity  is 
secured  by  straining  them  over  their  pulleys  with  a  weight,  or 
spring.  Another  method  is  to  fit  a  back  to  the  blade,  as  in  tenon 
(Fig.  94),  and  dovetail  saws,  hence  termed  back  saws,  the  only 
objection  to  which  is  that  the  blade  cannot  pass  right  through, 
and  into  stuff  thicker  than  its  own  depth,  and  is  therefore 
unsuitable  for  cutting  down  boards.  In  the  hand-saws,  cross¬ 
cuts,  turning-saws,  and  circulars,  rigidity  is  obtained  by  thicken¬ 
ing  the  blades  sufficiently,  but  making  them  no  thicker  than  is 
actually  necessary,  and  as  a  thick  blade  works  heavily,  and  is 
productive  of  much  friction,  this  is  lessened  by  reducing  the 
thickness  from  the  cutting  edges  backw^ards,  or  in  the  circular 
saws,  from  circumference  to  centre. 


The  grinding  of  a  saw  blade  is  an  important  matter,  the  ease 
and  rapidity  of  working  depending  very  much  on  this.  The  thick¬ 
ness  of  the  blade  must  taper  back  from  the  teeth  towards  the  back, 
and  also  from  the  end  towards  the  handle.  Fig.  97  shows  the 
varying  thicknesses  under  this  system,  the  measurements  being 
indicated  at  various  locations,  a,  b,  c,  d.  The  measurements 
w’ere  taken  by  Messrs  Chas.  Strelinger  &  Co.  with  a  micrometer 
caliper,  and  are  given  as  representative  of  a  high  grade  saw. 

Saws,  as  supplied  by  the  makers,  are  generally  sent  suitable 
for  a  given  class  of  timber.  But  repeated  re-sharpenings,  in  the 
case  of  circular  saws,  make  the  teeth,  or  the  tooth  spaces  smaller, 
because  the  same  number  of  teeth  remain  around  a  reduced 
diameter.  Then  it  is  better  to  use  the  saw's  for  some  other  kind 
of  work.  Or,  every  alternative  tooth  can  be  knocked  out,  or 
ground  out. 

The  degree  of  set  of  saw  teeth  varies  from  almost  nothing,  in 
the  case  of  saws  used  for  ripping  in  dry,  hard  woods,  to  larger 


84 


TOOLS. 


amounts  in  those  cutting  soft,  wet  logs,  and  in  most  that  are  used 
for  cross-cutting.  No  rule  can  be  laid  down,  but  varying  amounts 
of  set  are  given,  and  saws  selected  for  the  duties  which  they  have 
to  perform. 

Saw  teeth  are  kept  in  order  by  re-sharpening,  and  re-setting, 
and  here  good  tools  often  get  spoiled.  Minute  inaccuracies  affect 
the  working  of  saws,  and  these  become  cumulative.  Slight  varia¬ 
tions  in  the  sizes  of  the  teeth  do  not  matter,  though  they  look 
unsightly,  but  minute  differences  in  their  heights,  and  in  the 
amount  of  their  set  soon  show  themselves  in  bad  work. 

There  may  be  little  apparent  difference  between  a  saw  that 
works  well  and  one  that  does  not.  A  sharp  tool  may  work  badly, 
for  no  saw  will  cut  sweetly  if  the  set  is  irregular,  no  matter  how 
sharp  it  is.  On  the  regularity  and  the  amount  of  this  the  best 


results  depend.  Badly  set  saws  cannot  be  prevented  from  hitching 
in  the  stuff,  and  this  evil  is  more  pronounced  in  cutting  across, 
than  with  the  grain,  and  in  cutting  harsh  and  hard  woods  than 
straight-grained  soft  kinds. 

The  amount  of  set  which  is  imparted  to  teeth  is  varied  to  suit 
different  conditions.  In  a  tool  used  for  general  service  an  average 
is  struck.  But  two  saws  at  least  are  required  when  regular  work 
is  being  performed — one  for  ripping  with  the  grain,  and  one  for 
cross-cutting.  Another  may  be  well  added  for  cross-cutting  very 
wet  and  thick  wood  ;  this  one  having  the  maximum  amount  of  set. 

Irregular  setting  is  of  two  kinds :  in  one  it  is  variable  from 
tooth  to  tooth  ;  in  the  other  it  is  in  excess  all  on  one  side,  and 
insufficient  all  on  the  other,  though  regular  for  each  one  side. 
Both  are  common  errors.  The  effect  of  the  first  is  to  throw  more 
work  on  the  high  teeth  than  on  the  others,  and  dull  them  sooner* 


SAWS. 


85 


The  effect  of  the  second  is  to  cause  the  saw  to  “  run  ”  sideways  in 
the  direction  of  the  largest  amount  of  set.  This,  in  fact,  is  some¬ 
times  done  purposely,  when  the  blade  of  a  circular  saw  is  per¬ 
manently  buckled,  in  order  to  counteract  the  effect  of  the  latter. 


Setting  is  done  either  by  the  hammer  and  set-block,  or  with  a 
bending  appliance.  Besides  these  there  are  some  special  articles 
sold  for  the  purpose.  A  professional  saw-sharpener  almost  invari¬ 
ably  employs  the  first  named,  an  amateur 
and  many  workmen  the  second.  The 
strong  objection  to  the  latter  (Fig.  98 
showing  one  of  the  commonest  types)  is 
that  it  is  impossible  to  regulate  the 
amount  for  each  separate  tooth  with  exact 
precision  by  bending  it  with  the  set. 

Much  practice  is  necessary  to  handle  this 
so  as  to  produce  a  fair  approximation  to 
uniformity  in  the  teeth,  unless  a  sliding 
guide  is  used.  Another  objection  is  that 
the  setting  is  done  by  a  gradual  bending 
of  the  tooth,  instead  of  a  sharp  deflection, 
starting  from  the  root.  Using  the  hammer 
(Fig.  99),  these  evils  are  avoided.  The 
saw  blade  being  held  in  one  hand  at  an 
angle  which  must  not  vary  materially,  the 
setting  of  the  teeth,  each  by  a  single  sharp 
hammer-blow,  will  be  practically  uniform 

(Fig.  1 00),  and  the  bending  will  start  sharply  from  the  root.  The 
whole  of  the  setting  down  one  side — t.e.,  of  every  alternate  tooth 
— is  done  first,  and  then  that  of  the  other  side,  both  to  save  time 
and  secure  uniformity  of  results. 


Fig.  100. 


86 


TOOLS. 


Another  method  which  is  often  practised  for  fine-toothed  tenon, 
and  dovetail  saws,  is  to  lay  the  blade  flat  on  a  block  of  hard 
wood,  end  grain  up,  and  set  the  teeth  with  a  common  brad  punch  ; 
the  wood  yields  sufficiently  to  allow  the  teeth  to  take  their  set, 
and  without  the  slightest  elasticity,  the  latter  being  a  frequent 
cause  of  fracture  when  bending  with  a  saw-set.  Although  the 
block  affords  no  guide  for  the  amount  of  set  imparted,  it  becomes 
easy  to  regulate  the  force  of  each  blow  with  sufficient  uniformity 
to  produce  uniform  setting. 

Another  plan  is  to  bevel  the  edge  of  a  block  of  iron,  and  lay 
the  saw  on  it,  with  the  teeth  just  over  the  bevelled  edge,  and 
strike  the  teeth  with  a  setting  hammer.  This  ensures  uniformity. 
A  single  square  block  may  have  its  four  edges  bevelled  differently, 
to  suit  saws  having  different  degrees  of  set,  and  height  of  tooth. 


Another  device  is  shown  in  Figs.  loi  and  102,  where  a  is  a 
block  of  hard  wood,  b  a  plate  of  steel  grooved  for  four  different 
sets,  &c. ;  c  a  steel  punch  dropping  loosely  into  a  hole,  in  the 
bottom  of  which  is  an  indiarubber  cube,  which  keeps  the  punch 
just  above  the  saw  teeth,  which  cube,  however,  yields  readily  to 
the  pressure  of  the  punch  when  it  is  tapped  smartly  with  a 
hammer.  The  punch  is  brought  down  on  the  saw  teeth,  instead 
of  the  hammer  direct,  an  advantage  which  is  apparent  to  those 
who  have  experienced  how  a  falsely  directed  blow  will  knock  two 
consecutive  teeth,  instead  of  alternate  ones,  in  the  same  direction. 
Here  the  tooth  is  brought  close  under  the  punch  before  the  latter 
is  struck,  so  that  it  is  impossible  to  mistake  one’s  aim.  The  four 
faces  of  the  punch  being  bevelled  to  correspond  with  their 


SAWS. 


87 


respective  set  angles,  and  being  duly  proportioned  in  size  for 
larger  or  smaller  saws,  simply  bend  the  teeth  without  thinning 
them  down  at  the  points,  and  are  capable  of  setting  band  saws, 
hand-saws,  small  circular,  panel,  and  tenon  saws. 

For  those  who  are  afraid  to  trust  to  the  eye  and  hand  in  exact 
setting,  there  are  various  handy  devices  and  tools  made,  one  only 
of  which  need  be  noticed,  the  Morrill  saw  set  (Fig.  103).  Pressure 
on  the  handle  a  pushes  the  plunger  b  against  the  tooth,  and  the 
spring  pulls  it  back  again  on  the  release 
of  the  hand.  The  amount  of  set  to  be 
imparted  is  adjusted  by  the  anvil  c,  which 
can  be  moved  up  and  down  by  its  screw. 

The  chief  advantage  of  the  set  shown  is 
the  uniformity  of  its  results. 

The  test  of  regular  setting  is  to  hold 
the  saw,  end-on  to  the  eye,  and  on  casting 
the  latter  down  the  teeth,  it  will  be 
readily  seen  whether  any  of  them  stand 
out  beyond  the  rest.  A  more  accurate 
test  is  to  lay  a  fine  needle  in  the  groove 
formed  by  the  laying  over  of  the  teeth, 
and  incline  the  saw.  If  the  needle  runs 
down,  the  set  is  pretty  regular;  if  not, 
some  teeth  block  the  way.  \ 

Before  sharpening  saws,  the  teeth  are 
topped,  circular  saws  by  stoning,  other 
kinds  by  filing.  The  stone — any  piece 
of  hard  material,  as  millstone,  or  pennant 
— is  held  in  the  hands  before  the  revolving- 
saw,  and  brought  in  contact  with  the  tips. 

No  more  is  taken  off  than  just  suffices  to 
reduce  the  highest  teeth  to  the  level  of 
the  lowest.  The  reduced  teeth  will  be  left  with  little  bright  facets, 
which  are  the  guides  to  which  filing  has  to  be  done. 

In  hand-saws,  pit,  frame,  and  cross-cut  saws,  a  file  is  used,  a 
three-square  file,  or  a  flat  gulleting  file,  passed  down  the  teeth,  or 
in  the  direction  of  hook,  a  few  times,  until  the  topping  is  com¬ 
plete.  There  is  just  the  slight  risk  of  the  file  canting  over,  and 
taking  more  off  the  teeth  on  the  one  side  than  on  the  other.  To 
prevent  this  a  file  can  be  mounted  and  kept  for  this  work— Fig. 


88 


TOOLS. 


104),  A  being  the  file,  b  a  packing  piece,  the  file  being  too  hard  to 
drill  for  screws,  c  the  screws  for  pinching  a  and  b  on  the  block  d, 
of  about  1 1  in.  square,  by  6  in.  or  8  in.  long. 
The  vertical  face  lies  against  the  plate  of  the 
saw. 

With  regard  to  the  height  of  teeth,  it  is 
obvious  that  the  case  is  like  that  of  milling 
cutters,  uniformity  in  height  of  which  is  essential 
if  all  the  teeth  are  to  be  operative.  If  they  are 
irregular,  and  one-fourth  of  the  number  are  below  the  rest,  they 
will  be  doing  only  a  part  of  their  work,  or  be  absolutely  idle, 
according  to  the  depth  of  cut.  In  frame  saws,  hand-saws,  and 
cross-cuts,  this  is  just  as  true  as  in  circulars. 

The  forms  of  the  various  teeth  involve  differences  in  sharpening 
them.  The  triangular,  or  three-square  file  can  only  be  used  pro¬ 
perly  on  those  teeth  the  adjacent  faces  of  which  make  angles  of 
60°  with  each  other.  For  other  teeth  the  various  mill-saw  files 
are  provided. 


Fig.  105. 


Fig.  106. 


The  files  used  are  tapered,  and  parallel,  single,  and  double 
cut,  according  to  the  work  they  have  to  do.  Most  of  them  are 
single  cut,  the  double  cut  being  used  chiefly  for  the  smaller  saws. 
For  purely  triangular  teeth  the  three-square  files  are  employed, 
tapered  for  small  saws,  parallel  or  blunt  for  large  ones.  When  a 
saw  is  gulleted  it  is  generally  necessary  to  use  a  round  or  gulleting 
file  for  the  roots,  and  one  of  the  flat  or  mill-saw  files  for  the  backs 
and  fronts.  In  some  cases,  however,  a  flat  file  with  one  edge  or 
with  both  convex  is  employed  to  file  flat  and  gullet  at  once.  A 


SA  WS.  '  89 

half-round  file — the  pit-saw  file — is  also  used  for  teeth  with 
gullets. 

Saws  used  for  cutting  timber  must  not  be  filed  straight  across, 
or  they  would  work  heavily  and  slowly.  Only  a  keen  corner  is 
left  standing  up  on  the  outside  of  each  tooth  (see  the  enlarged 
section,  Fig.  105),  and  this  is  produced  by  setting  the  file  at  a 
double  angle.  One  of  these  is  an  angle  departing  from  the  square- 


Fig.  107. 


across  position ;  the  other  from  the  horizontal,  so  that  the  file  is 
held  askew  in  two  directions.  The  first  is  the  principal  angle,  and 
it  varies  in  saws  for  cutting  hard  and  soft  woods,  the  greater  angle 
being  given  for  the  latter.  One  does  not  measure  these  angles — the 
eye  is  sole  guide;  but  if  tested,  they  will  be  found  to  average  about 
70"  from  the  saw-blade,  or  20°  from  the  square-across  position,  and 
about  10°  from  the  horizontal.  The  effect  on  the  shape  of  the  teeth 


Fig.  108. 


is  seen  in  Figs.  105,  106,  107,  and  108.  Only  the  back  of  each 
tooth  receives  the  pressure  of  the  file  in  Fig.  106,  though  a  trifle 
unavoidably  comes  off  the  front  also.  The  fronts  of  teeth  are 
only  specially  reduced  if  the  pitch  happens  to  have  got  irregular. 
All  the  teeth  that  lean  away  from  the  file  are  treated  at  once,  and 
then  the  saw  is  reversed  in  the  vice,  and  the  alternate  ones  are 
done.  That  uniformity  of  angle  is  thus  secured  which  conduces 


90 


TOOLS. 


to  sweetness  of  cutting.  In  each  tooth  the  shearing  principle  is 
embodied,  the  slope  of  the  tooth  edge  producing  a  diagonal  cut, 
instead  of  one  straight  across.  The  difference  in  sweetness  of 
working  is  similar  to  that  between  a  square  mouth  and  a  skew  mouth 
rebate  plane.  In  these  views  it  is  seen  that  the  outer  points  of  the 
teeth  (a,  a.  Fig.  105  ),  enter  and  sever  the  grain  before  the  sloping 
edges  follow  to  remove  the  dust.  Fig.  106  shows  the  teeth  of  a 
hand-saw.  Figs.  107  and  108  show  the  difference  in  the  teeth  of 
circular  saws  for  hard,  and  soft  wood  respectively;  Fig.  109  is  a 

band  saw  blade. 

When  a  hand-saw  is  thus  set  and 
sharpened  regularly  it  will  not  hitch, 
if  handled  with  reasonable  precision, 
excepting  for  an  instant  at  the  com¬ 
mencement  of  a  cut,  and  that  may 
be  easily  prevented  by  holding  the  saw  lightly  just  at  the  start. 

Of  late  years  a  number  of  machines  have  been  introduced  for 
the  automatic  sharpening  of  machine  saws,  both  band  and  circu¬ 
lar,  using  emery  wheels  in  place  of  files.  Absolute  uniformity  is 
thus  secured. 

Inseparable  from  sharpening  is  the  work  of  gulleting  (Fig.  93, 
p.  81,  and  Figs.  107,  108).  To  continue  topping  and  sharpening 
without  gulleting  results  in  short  teeth,  and  insufficient  clearance 
for  sawdust.  So  that  after  a  saw  has  been  resharpened  from  three 
to  half-a-dozen  times,  the  teeth  are  deepened  in  the  gullets.  This 
of  course  applies  to  teeth  that  are  not  triangular  in  shape,  but  have 
concave,  or  flat  roots.  A  hand- saw  for  instance,  or  a  triangular 
toothed  cross-cut  is  deepened  by  the  same  filing  which  sharpens. 
But  even  in  these  it  is  not  unusual  to  find  teeth  become  shallower 
in  time,  due  to  the  unconscious  harder  pressure  exercised  when 
filing  towards  the  upper  portions  of  the  teeth,  done  to  expedite 
sharpening.  In  hollow  gulleting,  the  half-round  edge  of  a  gulleting 
file  is  used,  or  a  blunt  pointed  parallel  round  file.  This  is  the 
method  where  gulleting  machines  are  not  available.  Many  shops 
have  these,  and  then  an  emery  wheel  with  convex  edge  reduces 
the  metal  with  much  greater  rapidity  than  any  filing  is  capable  of. 

Forcing  a  saw,  or  forcing  the  work  to  a  saw  does  positive 
damage,  besides  that  of  lost  energy.  It  makes  the  saw  hot,  and 
that  produces  buckle  in  a  circular  saw,  and  overstrain  in  band 
saws,  and  inaccurate  cutting  in  both. 


Fig.  109. 


SAWS. 


91 


The  first  makes  itself  apparent  in  a  wabbling  motion,  and  a 
loud  disagreeable  clanging  sound  "when  the  stuff  leaves  the  saw 
free,  and  it  may,  or  may  not  leave  permanent  buckle  after  the  saw 
has  cooled.  The  best  plan  if  this  happens,  is  to  let  the  saw  run 
awhile  until  the  heat  has  become  equalised,  and  then  dissipated. 
If  the  buckle  remains,  the  plate  must  be  hammered  by  a  qualified 
man.  Frequently  the  buckle  can  be  got  out  by  pressing  the  end 
of  a  piece  of  wood  hard  against  the  blade  of  the  saw  in  the 
vicinity  of  the  spindle,  and  thence  outwards  slowly  towards  the 
teeth,  but  stopping  short  of  them.  The  object  of  this  is  to  expand 
the  saw  around  the  spindle,  and  so  equalise  the  temperature  there 
with  that  of  the  teeth,  and  parts  adjacent.  A  strained  band  saw 
ceases  to  run  like  a  fine  line,  wabbling  in  a  more  or  less  wavy 
fashion. 

Too  rough  setting  will  buckle  a  saw  next  the  teeth.  Buckle 
is  often  magnified  by  an  attempt  to  take  out  a  slight  amount,  by 
careless  hammering.  The  way  to  remove  it  is  to  hammer,  and 
spread  the  metal  in  the  vicinity  of  the  buckle,  allowing  the  latter 
to  spread  itself  out. 

Any  machine  saw,  whether  circular,  or  band,  requires  to  be 
packed  close  to  the  portion  that  is  cutting.  A  circular,  if  of  large 
size,  is  also  packed  in  the  rear.  Without  this  precaution,  it  would 
be  impossible  to  use  the  thin  blades  that  are  necessary  to  the 
economical  conversion  of  timber.  A  thin  blade  with  a  moderate 
amount  of  set  is  the  ideal  tool. 

With  regard  to  the  adaptability  of  saws  to  their  work,  the  one 
with  the  coarsest  teeth  that  is  suitable  for  a  job  should  be  used  as 
a  matter  of  economy.  To  employ  a  fine  saw,  excepting  for  fine 
work,  is  wasteful  of  time.  It  is  not  economical  to  cross-cut  thick 
stuff  with  a  common  hand-saw,  while  a  rip  saw  is  quite  unfit  for 
such  work.  It  is  wasteful  to  cross-cut  thick  stuff  with  a  small 
tenon  saw,  or  to  use  a  dovetail  saw  for  ordinary  bench  work.  In 
proportion  as  the  teeth  become  finer  and  more  numerous,  their 
capacity  for  removing  dust  is  lessened.  And  although  fine  teeth 
are  wanted  for  thin  stuff,  and  exact  sawing  to  line,  they  are  not  to 
be  employed  for  the  opposite  conditions,  simply  because  they 
happen  to  be  so  easily  operated. 

With  respect  to  the  methods  of  using  hand  and  bench  saws, 
the  first  point  is  to  have  the  wood  secure.  The  sawing  stool  or 
trestle  is  used  to  lay  the  board  on  for  the  ordinary  work  of  ripping 


92 


TOOLS. 


and  cross-cutting,  two  stools  being  used  for  long  pieces,  one  for 
short  ones,  and  the  workman  lays  his  right  knee,  or  his  left  hand 
on  the  board  to  prevent  it  from  rising.  The  saw  is  held  at  an 
angle  of  about  65“  with  the  face  of  the  board.  Short  pieces  can 
often  be  cut  closer  to  lines  when  held  perpendicularly  in  the 
bench  vice,  as  in  sawing  down  the  shoulders  of  tenons.  The 
same  position  is  adopted  when  using  the  compass,  keyhole,  or  bow 
saws.  The  work  is  held  steadily,  the  lines  are  seen  better,  and 
both  hands  are  left  free  to  operate  the  saws. 

The  tenon  and  dovetail  saws  are  employed  on  the  bench 
mostly,  the  work  being  laid  thereon.  But  resistance  to  the  saw 
is  generally  afforded  by  the  bench  hook,  or  the  shooting  board,  or 
by  the  vice,  or  in  some  cases  by  the  angle  board. 

A  difficulty  which  unskilled  amateurs  and  clumsy  work¬ 


men  encounter  is  that  of  sawing  exactly  to  a  line,  and  plumb. 
You  see  a  cut  started  all  wobbly,  in  the  attempt  to  guide  the 
saw  straight,  and  to  the  line.  This  will  also  occur  most  readily  in 
the  case  of  a  saw  having  too  much  set  for  its  work,  as,  for  instance, 
a  hand-saw  set  coarsely  to  cross-cut  but  used  for  ripping.  This 
difficulty  can  be  avoided  by  sighting  the  saw  correctly  before  be¬ 
ginning  to  cut.  To  saw  plumb  comes  by  practice.  Apprentices 
may  set  a  square  on  the  board  and  up  the  blade  of  the  saw ;  but 
they  must  soon  discard  that  unless  they  want  to  be  laughed  at. 

Figs,  no  and  in  show  two  forms  of  mitre  blocks,  in  wood, 
and  metal  respectively,  by  which  the  movement  of  tenon  saws  is 
controlled  at  an  angle  of  45°.  When  any  large  amount  of  sawing 
has  to  be  done  either  to  length,  or  angle,  by  hand  or  machine, 
mechanical  aids  are  utilised. 


CHAPTER  IX. 


Files. 

The  Forms  of  the  Teeth — Mode  of  Action — General  Employment  of  Files- 
Sections — Derivations  of — Longitudinal  Forms — Degrees  of  Coarseness  of 
Cut — Terms — Special  Files — Length — Special  Handling. 

Files  and  rasps  must  be  classed  with  the  scrapes,  as  a 
glance  at  the  enlarged  sectional  form  of  the  teeth  (Fig. 
1 1 2)  will  show.  A  keen  file  tooth  will  not  retain  its 
cutting  capacity  long,  the  tips  becoming  broken  off  almost 
immediately.  A  file  is  therefore  a  collection  of  scrapes,  just  as 
the  ordinary  saw  is  a  series  of  chisels. 

A  file  possesses  a  shearing  action, 
because  the  rows  of  teeth  are 
arranged  diagonally,  besides  which 
the  workman  often  gives  a  diagonal 
traverse  to  the  tool  in  use.  The  teeth  of  files  are  cut  by  hand, 
and  by  machine,  .^t  one  time  the  prejudice  against  the  latter 
was  very  strong,  but  they  are  gradually  ousting  their  rivals  from 
the  market. 

Files  and  rasps  number  probably  from  two  to  three  thousand 
different  sizes.  They  are  employed  in  nearly  all  trades,  both 
for  metal,  and  woodworking.  The  largest  are  used  by  the 
engineer,  and  the  smallest  by  watchmakers,  and  locksmiths. 
Cabinetmakers  and  carvers  employ  them,  and  saw  sharpeners,  and 
farriers. 

The  principal  points  about  any  file  or  rasp  are  :  The  manner 
in  which  its  teeth  are  cut,  their  degree  of  coarseness,  the  longi¬ 
tudinal  shape,  the  section,  and  the  length.  The  figures  illustrate 
these  cardinal  points. 

With  regard  to  the  sections,  we  see  that  files  are  in  many 
cases  the  counterpart  of  the  forms  which  they  have  to  produce. 


Fig.  1 1 2. 


94 


TOOLS. 


The  flat  files  are  obviously  intended  for  flat  surfaces.  But  they 
will  of  course  produce  convexities.  If  concavities  have  to  be 
filed,  the  half-round,  and  similar  tools  are  used,  while  in  some 
cases  longitudinal  concavities  are  produced,  as  in  the  case  of 
riffler  files,  besides  which,  engineers  bend  or  crank  their  files  for 
special  purposes.  In  other  cases  files  are  used  to  impart  exact 
angles. 

Looking  at  Fig.  113,  we  see  that  sections  derived  from  the 
rectangle  are  the  square  files  a,  the  flat  files  b,  which  occur  in 
various  thicknesses,  and  longitudinal  outlines.  A  special  flat  file 


is  the  mill  file  c,  which  is  thinner  for  a  given  width  than  the  flat 
file  B.  A  very  thick  flat  file  d  is  a  pillar  file,  while  a  very  thin 
one  E  is  a  warding  file.  Often  flat  files  have  both,  or  one  edge 
rounding,  as  at  f,  g.  Rasps  are  made  in  similar  sections  to  the 
files.  Sections  derived  from  the  circle  include  the  round  files  h, 
the  frame  saw,  or  pit-saw  file  j,  the  half-round  k,  the  cabinet  files 
L,  M,  the  double  half-rounds  n,  o,  whieh  contain  different  curva¬ 
tures  on  opposite  faces.  Sections  derived  from  the  triangle  are 
the  three-cornered,  or  three-square  file  p,  the  cant  file  Q,  the 
slitting,  or  feather-edge  file  r,  and  the  knife  file  s.  Compounded 


FILES. 


95 


of  the  square  and  triangle  are  the  swaged  reaper  files  t  and  u, 
and  the  reaper  knife  files  v,  w. 


ABC  D  E  F  Q  H  j 
Fig.  1 14. 

Coming  to  the  longitudinal  forms  of  files,  we  have  in  Fig,  114 
first,  A,  B,  c.  A  is  a  hand  file,  which  may  be  nearly,  or  quite 
parallel.  When  a  file  is  parallel  throughout  its 
length  it  is  termed  blunt  pointed,  to  distinguish  it 
from  the  ordinary  equalling  file,  which  always  has 
a  slight  curvature  lengthwise,  b  is  a  tapered  file. 

It  may  be  nearly  straight-tapered,  or  of  a  bellied 
form,  as  in  the  figure.  But  any  such  file  is  always 
considerably  smaller  at  the  point  than  it  is  next  the 
tang,  differing  therefore  from  a.  The  square  file  c 
is  tapered  in  the  figure  and  bellied.  It  is  also 
made  parallel,  or  blunt,  d  and  e  represent  respec¬ 
tively  the  three-square  file,  and  the  three-square 
blunt  saw  file,  one  being  tapered  and  bellied,  the 
other  parallel,  f  and  g  are  round  files,  the  first 
being  commonly  termed  a  rat-tail,  the  second  a 
gulleting,  being  used  by  sawyers,  for  filing  the  roots 
or  gullets  of  large  saws,  h  is  a  common  half-round, 
and  bellied  file ;  j  is  a  parallel  half-round,  also  termed  a  pit-saw, 
or  frame-saw  file.  Most  of  these  can  be  had  single,  or  double  cut, 
and  also  as  rasps,  the  difference  of  which  is  shown  in  Fig.  115, 


Fig.  115. 


<G 


99 


TOOLS. 


A  being  the  double,  b  the  single  cut,  and  c  the  rasp  cut.  In  a  the 
teeth  are  formed  by  the  intersection  of  crossing  chisel  cuts,  so 
producing  isolated  points.  In  b  the  lines  run  singly  in  one  direc¬ 
tion,  forming  continuous  cutting  edges,  a  and  b  are  cut  with 
chisels,  the  rasp  teeth  c  are  thrown  up  by  a  punch.  Most  files 
used  by  metal  workers  are  of  double  cut  type.  The  single,  or  float 
cut  are  largely  used  by  sawyers  for  tooth  sharpening.  Rasps  are 
used  by  cabinetmakers,  carvers,  farriers,  and  core  makers. 

The  degrees  of  coarseness  of  cut  are  designated  by  the  following 
terms : — Rough,  Middle  Cut,  Bastard  Cut,  Second  Cut,  Smooth, 
Double  Dead  Smooth.  The  foregoing  relates  to  double  cut  files. 
In  single  cut  the  corresponding  terms  are  Rough,  Middle,  New 
Cut,  Smooth  Float,  Second  Cut,  and  Smooth.  In  rasps,  the 
terms  are  Horse,  Rough,  Middle,  Bastard,  Second  Cut,  Smooth. 
These  terms  are  relative.  The  coarseness  designated  by  any  one 
of  these  terms  increases  in  proportion  to  the  length  of  a  file. 
So  that  a  coarse  file  in  one  size  would  have  a  number  of  teeth 
per  lineal  inch  corresponding  with  a  second  cut  in  another 
length.  A  12  in.  file  is  generally  taken  as  a  standard  in  esti¬ 
mating  the  number  of  teeth  per  inch.  Rifflers  are  double-ended 
curved  files,  or  rasps,  used  by  cabinetmakers  and  carvers.  Some¬ 
times  they  are  single-ended,  and  used  with  wooden  handles  like 
the  majority  of  files. 

There  is  a  certain  class  of  file,  the  safe  edge,  in  which  one 
edge  is  left  uncut.  It  occurs  in  the  taper,  and  parallel  hand  files, 
and  in  some  of  those  used  for  saw  sharpening.  Its  object  is,  of 
course,  to  prevent  material  from  being  removed  from  some  por¬ 
tions  of  a  piece  of  work  while  others  are  being  filed.  Some  files 
have  special  names  which  designate  their  exact  uses,  such  as 
cottar,  warding,  slitting,  escapement,  pivot,  and  balance  files. 

Generally  speaking,  files  range  in  length  from  2  to  24  in.  but 
this  depends  largely  upon  type;  16  or  17  in.  is  the  usual  limit, 
and  many  types  do  not  go  beyond  8  or  10  in.  ;  while  in  others 
the  limit  is  from  2  to  3  in. 

For  filing  large  flat  surfaces,  the  handle  of  the  file  must 
necessarily  be  elevated,  in  order  to  enable  the  worker’s  hand  to 
clear  the  surface.  This  may  be  done  by  either  bending  the  tang 
upwards  to  an  angle  sufficient  to  raise  the  handle  off  the  job,  or 
by  cranking  the  tang — that  is,  bending  it  upwards,  and  then  along 
horizontally  again.  This  gives  a  more  direct  thrust  to  the  file  than 


FILES. 


97 


simply  bending  at  an  angle.  Bending  may  be  dispensed  with  by 
employing  the  device  in  Fig.  ii6.  A  special  handle  is  made  by 
bending  round  rod  as  shown,  one 
end  being  tapped  into  an  ordinary 
hexagon  nut.  The  latter  is  filed  out 
to  fit  the  tang  of  the  file,  and  driven 
tightly  on  the  latter,  the  plain  end 
of  the  rod  resting  on  the  file  a  little 
way  up.  Several  variations  on  this 
common  device  are  employed,  but 
their  principle  is  similar. 

When  the  teeth  of  files  become  choked  or  “pinny,”  they  are 
brushed  clean  with  card  wire.  Specially  obstinate  bits  of  metal 
must  be  picked  out  with  a  pointed  bit  of  wire. 


Fig.  ii6. 


CHAPTER  X. 


Milling  Cutters. 

More  Economical  than  Single-Edged  Tools — Multiplication  of  Edges — Dis¬ 
counted  by  Shallowness  of  Cutting — Rake  —  Durability — Spiral  Twist — 
Period  of  Rest  during  Revolution — Question  of  Speeds — How  effected — 
Average  Rates — The  work  of  each  Tooth — Necessity  of  keeping  edges 
sharp-— Heavy  feeds — Pitching  of  Teeth — Direction  of  Feeding — Varieties 
in  forms  of  Cutters— Face  and  Edge  Mills— Their  proper  Spheres — Gang 
IMilling — Devices  adopted  in  Building  up— Milling  Parallel  Grooves — 
The  Wear  of  the  Mills — Combinations  of  Edges — Angular  Mills — The 
case  of  Profiled  Forms — Examples— Profile  Milling  compared  with 
Grinding — and  Planing — Profiling  Machines — Face  Mills  with  Inserted 
Teeth — Methods  of  Insertion— and  Securing — Advantages — Staggered 
Teeth  in  Solid  Mills — Taper  Shank  Mills — Formed  Mills — Lubrication 
of  Cutters—  Pickling. 

The  reason  why  milling  cutters  effect  more  economy  in  time 
than  single-edged  tools  like  those  used  on  planer,  shaper, 
and  slotter,  is  that  they  embody  a  multiplication  of  tool 
edges.  An  ordinary  roughing  tool  cuts  by  means  of  its  single 
point,  a  finishing  tool  by  its  narrow  edge.  Each  removes  a 
shaving  equal  to  the  width  of  the  point,  or  edge  which  is 
operating,  and  no  wider.  To  remove  material  from  a  surface 
of  several  inches  in  width,  a  traverse  movement  must  be  given 
to  such  a  tool.  Milling  cutters  are  simply  a  collection  of  numer¬ 
ous  cutting  edges  which  operate  in  rapid  succession  on  the  same 
surface,  and  they  will  act  over  a  width  of  several  inches  at  once, 
without  the  loss  of  time  involved  in  traverse  feed. 

On  the  other  hand,  it  is  to  be  remembered  that  very  deep 
roughing  cuts  cannot  be  taken  with  broad  milling  cutters,  because, 
as  usually  formed,  they  are  scraping  tools — that  is,  tools  the  cut¬ 
ting  faces  of  which  stand  perpendicularly  to  the  face  of  the  work, 
whereas  machine  roughing  tools  have  a  large  amount  of  top  rake, 
by  reason  of  which  they  are  capable  of  much  penetration.  But 
this  disadvantage  is  only  a  slight  set-off  against  the  advantages  to 


MILLING  CUTTERS. 


99 


be  derived  from  the  use  of  many  cutting  edges  of  great  width. 
Mills  must  be  so  formed  that  they  will  give  good  mean,  or  aver¬ 
age  results  on  all  metals  and  alloys,  and 
therefore  suitable  for  iron  and  steel,  for 
brass  and  gun  metal,  the  same  cutters 
being  generally  used  on  all  alike.  As 
they  generally  have  faces  perpendicular 
to  the  face  of  the  work  which  is  being 
operated  upon,  this  formation 
limits  the  depth  of  the 
cut,  and  thickness  of  chip 
removed. 

But  depth  of  cut  in  this 

case  is  of  less  importance  than  durability  of  the  cutting 
edges.  When  the  edges  become  dulled,  regrinding  is  a 
more  tedious  process  than  that  of  single-edged  tools,  and 
it  is  therefpre  more  economical  to  preserve  the  cutting 
edges  as  long  as  possible,  even  at  the  sacrifice  of  some 
penetrative  power.  And  this  loss  is  much  more  than 
compensated  for  by  the  multiplication  of  those  edges. 
So  that  here,  as  in  most  other  matters,  practical  con¬ 
ditions  rather  than  theoretical  considerations,  settle  the 
ultimate  forms  of  the  cutters. 

In  all  but  the  narrowest  mills,  the  cutting  resistance 
is  diminished,  and  a  smoother  surface  produced  by  im- 
Fig.  1 1 8.  parting  a  spiral  twist  to  the  teeth,  producing  a  shearing 
cut.  In  some  of  large  diameter  and  width,  the  principle 
IS  still  further  developed  by  breaking  up  the  spiral  into  numerous 


Fig.  1 19. 


short  teeth  (Fig.  154,  p.  117),  and  also  by  arranging  them  in 
both  right  and  left  hand  spirals  (Fig.  119),  similarly  to  the  teeth 


lOO 


TOOLS. 


of  double  helical  wheels.  The  resistance  is  thereby  much  reduced, 
and  deeper  chips  can  be  taken,  while  experience  has  proved  that 
the  short  cutters  do  not  become  broken,  as  it  was  anticipated 
they  might  be. 

There  is  an  important  distinction  between  the  edges  of  the 
milling  cutters,  and  the  single  tool-point  of  the  planing  and  allied 
machines.  It  is  that  the  single  tool-point  cuts  almost  continuously, 
its  only  period  of  rest  being  that  which  occurs  during  the  return 
or  non-cutting  stroke.  But  any  single  edge  of  the  milling  cutter 
is  inoperative  during  by  far  the  greater  portion  of  the  revolution 
of  the  mill.  It  has,  therefore,  a  much  longer  time  in  which  to 
cool  than  the  single  tool-point,  and  it  can  consequently  be  run 
faster ;  and  this  goes  a  long  way  towards  compensating  for 
diminished  cutting  power  due  to  the  absence  of  front  rake.  In 
this  respect  it  compares  most  favourably  with  the  single  cutting 
tool  used  in  planer  or  shaper,  which  is  cutting  during  about  two- 
thirds  of  the  time,  and  has  little  time  in  which  to  cool  off ;  and 
the  lathe  tool,  cutting  all  the  while. 

In  order  to  obtain  the  best  results  from  milling,  attention  must 
be  given  to  the  rates  of  speed,  by  varying  the  rate  of  revolution  of 
the  cone  spindle  to  suit  the  diameters  of  cutters.  The  rate  of 
surface  travel  in  feet  per  minute  is  the  important  matter,  just  as  it 
is  in  the  lathe,  and  other  machines.  Hence  the  belt  must  be  shifted 
with  any  material  alterations  in  the  diameter  of  cutters  used.  This 
is  an  obvious  matter,  but  one  which  is  frequently  neglected. 

So  many  causes  affect  speeds,  that  almost  every  job  must 
stand  by  itself.  There  is  the  question  of  the  condition  of  the 
cutters  themselves — whether  properly  formed,  whether  sharp,  or 
dull,  ground  regularly,  or  otherwise;  suitably  tempered  for  the 
class  of  work  on  which  they  have  to  operate,  or  not.  Then  there 
is  the  relation  of  speed-  to  depth  of  cut,  and  surface  feed,  the 
class  of  cutter  being  used,  the  nature  of  the  metal  or  alloy  being 
operated  on,  the  kind  of  work  being  done.  So  that  the  problem 
resolves  itself  generally  into  one  of  experience  in  given  classes  of 
jobs. 

Milling  cutters  can  be  run  generally  at  from  two  and  a  half  to 
about  three  times  the  cutting  speed  used  with  single-edged  tools. 
With  shallow  cuts,  and  moderate  feeds,  cast  iron  may  be  milled 
with  cutters  having  a  surface  speed  of  40  to  50  feet  a  minute, 
cast  steel  from  20  to  30,  wrought  iron  from  50  to  70,  and  brass 


MILLING  CUTTERS. 


lOI 


from  8o  to  120.  For  light  finishing  cuts  these  rates  may  be 
increased  by  from  50  to  100  per  cent.  Milling  cutters  are  being 
made  of  the  new  high  speed  steels,  with  higher  rates,  and  feeds. 

Cast  iron  is  milled  dry ;  other  metals  and  alloys,  with  water, 
or  preferably  oil. 

To  obtain  the  perfection  of  operation  from  mills,  it  is  obvious 
that  each  tooth  should  do  its  fair  share  of  work.  If  a  sixteenth 
of  an  inch  is  being  removed  at  one  revolution  of  a  mill,  and  it  has 
60  teeth,  it  means  that  each  tooth  should  be  removing  ^\jth  of 
yV  iri-  That  is  a  very  minute  thickness,  and  since  the  radial 
dimensions  of  the  teeth  may  well  differ  from  one  another  by  that 
amount,  or  more,  without  being  perceptible,  it  follows  that  the 
duty  of  cutting  may  devolve  on,  say,  10,  or  20  teeth  of  the  60.  If 
the  rate  of  feed  or  travel  has  been  speeded  to  suit  the  work  which 
a  perfect  mill  would  do,  that  is  a  mill  in  which  each  tooth  of  the 
60  would  be  cutting;  then  obviously  10  teeth  will  not  do  the 
work,  and  they  will  become  heated,  and  the  speed  will  have  to  be 
reduced.  Or,  again,  if  the  teeth  are  ground  practically  perfect, 
but  are  worked  after  they  have  become  dulled  by  use,  to 
save  the  trouble  of  re-grinding,  then  the  mill  will  become  over¬ 
heated,  and  the  speed  will  have  to  be  reduced. 

Milling  cutters  obviously  should  never  be  worked  until  their 
cutting  edges  are  dulled  so  much  as  to  be  very  visibly  so.  The 
passing  of  the  finger  lightly  over  the  edge,  which  should  be  very 
keen,  is  a  better  test  than  the  sight.  One  or  two  movements  of 
the  cutters  under  a  fine  grade  revolving  emery-wheel  will  restore 
the  edges. 

The  degree  of  stability  of  the  machine,  and  the  condition  of  the 
mill  will  make  a  difference  of  50  or  even  100  per  cent,  in  cutting 
feed.  If  a  high  feed  is  attempted  with  a  mill  in  bad  order,  the  belt 
will  slip,  or  the  teeth  break,  or  the  tool  chatter.  The  heavier  the 
feed  measured  in  depth  of  cut,  the  more  work  there  is  thrown  upon 
the  cutters,  and  the  greater  the  tendency  of  the  work  to  bend,  or 
spring  away  from  the  cutters,  or  vice  versa.  In  light,  unsupported 
work,  this  has  to  be  reckoned  with  quite  as  much  as  the  heating 
of  the  cutters,  because  their  profiles  will  not  be  accurately  repro¬ 
duced  on  surfaces  which  do  not  remain  in  rigid  contact  with  them. 
Hence  the  rate  of  feed,  and  depth  of  cut  are  affected  both  by  the 
stability  of  the  arbor  and  its  supports,  and  by  that  of  the  work, 
which  is  also  influenced  by  its  height  or  distance  from  the  table. 


102 


TOOLS. 


by  overhang,  by  its  own  rigidity,  and  similar  kindred  matters.  It 
is  therefore  of  little  use  to  give  rates  of  feed  and  travel  unless  with 
certain  machines  doing  certain  work.  The  limitation  to  the  speed 
and  feed  of  mills  is  also,  other  things  being  equal,  partly  that  due 
to  the  pitching  of  the  teeth.  The  limit  of  speed  appears  to  be 
that  at  which  the  teeth  become  choked  with  the  chips.  This  is 
the  condition  termed  “  crowding,”  in  which  the  mills  are  driven  so 
fast  that  the  chips  have  not  time  to  get  away  from  the  teeth. 
Until  this  is  reached,  the  higher  the  speed  and  feed  the  more 
economical  should  the  results  be  under  any  given  set  of  condi¬ 
tions. 

Mr  Addy  gave  a  rule  for  obtaining  the  pitch  of  the  teeth  of 
mills  of  all  diameters  from  4  to  15  in.  : 

Pitch  in  inches  =  (diameter  in  inches  x  8)  x  0.0625. 


Or  put  more  tersely  by  Mi  Gray  thus ;  “  The  number  of  teeth  in 
a  milling  cutter  should  be  one  hundred  times  the  pitch  in  inches. 
So  that  if  there  were  30  teeth  in  a  cutter,  the  pitch  would  be  0.3 
of  an  inch.  Actually  the  teeth  of  average  mills  range  between  about 
^  in.  and  |  in.  pitch. 

Some  controversy  has  arisen  respecting  the  better  method  of 
feeding  the  work,  whether  towards,  or  with  the  revolving  cutter, 
and  some  differences  of  opinion  between  people  well  qualified  by 
practice  to  form  a  judgment  on  the  matter  exists.  But  all  reason 
seems  in  favour  of  the  long-established  method  of  feeding  towards 
the  cutter.  Thus,  let  Fig.  120  represent  the  old  style  of  feeding, 
and  Fig.  121  the  other.  In  Fig.  12 1  the  depth  of  cut  is  least 
at  the  commencement  and  greatest  at  its  termination.  In  Fig.  120 


MILLING  CUTTERS. 


103 


the  depth  is  greatest  at  the  commencement.  The  arbor  would 
be  less  liable  to  chatter  in  the  first  case  than  in  the  second. 
In  Fig.  120  the  constant  pressure  of  the  work  tends  to  prevent 
vibration  in  the  arbor.  In  Fig.  121  the  tendency  is  to  v’ibrations 
of  varying  intensity,  throwing  the  mill  off  the  work,  and  causing 
chatter.  Again,  in  Fig.  120,  after  the  mill  has  struck  the 
work,  it  cuts  soft  metal  continuou.sly.  In  Fig.  121  it  is  con¬ 
tinually  cutting  from  the  skin  downwards,  which  soon  dulls  the 
"cutting  edges.  These  considerations  are  all  in  favour  of  the 
common  practice,  notwithstanding  that  the  experience  of  some 
men  has  declared  itself  in  favour  of  the  other  method. 

The  number  and  variety  of  milling  cutters  is  very  large.  They 
comprise  solid  cutters,  and  cutters  with  inserted  teeth ;  plain 
cutters  for  operating  on  plane  surfaces  by  their  sides,  and  by  their 
ends  on  one  surface  only  at  a  time,  combinations  of  plain  cutters 
for  operating  on  several  surfaces  simultaneously  ;  cutters  of  irre- 


Fig.  123. 


gular  outlines — curved,  angular,  symmetrical  in  form,  or  otherwise, 
for  various  classes  of  work,  made  either  solid,  or  composed  of 
several  mills  on  a  single  arbor.  The  solid  mills  range  from  -g-  in. 
or  ^  in.  in  diameter  up  to  6  in.  or  8  in.,  and  mills  with  inserted 
teeth  up  to  several  feet  for  exceptional  duty.  The  width  of  mills 
will  range  from  in.,  used  for  slitting,  up  to  a  couple  of  feet 
or  more,  being  limited  only  by  the  width  of  machines. 

The  primary  distinction  between  cutters  is  that  of  end  or  face 
mills,  and  edge  mills.  In  the  first  case,  the  end  of  the  mill  cuts  ; 
in  the  second,  the  edge.  The  first  cuts,  therefore,  in  a  plane  at 
right  angles  with  the  axis  of  rotation,  the  second  in  a  plane  parallel 
with  that  axis.  Each  is  better  adapted  for  some  kinds  of  work 
than  others,  but  each  is  also  used  indifferently  for  a  large  variety 
of  operations.  Thus,  for  example,  it  does  not  matter  as  regards 
ultimate  results  whether  a  cutter  produces  a  plane  surface  with 
the  end  mill  (Fig.  122)  or  with  the  edge  mill  (Fig.  123).  Neither 
would  the  results  be  different  if  the  edges  of  a  groove  were  cut  by 


104 


TOOLS. 


the  sides  of  an  end  mill  in  Fig.  124,  or  the  sides  of  an  edge  mill 
as  in  Fig.  j  25,  of  the  kind  shown  in  perspective  in  Figs.  126  and  127 
— and  these  examples  are  typical  of  many  which  occur  in  every¬ 
day  practice.  Neither  is  it  of  any  consequence  whether  plain 


faces  or  edges  occur  in  horizontal,  or  in  vertical  planes.  An  edge 
mill  (Fig.  128)  set  on  a  vertical  spindle,  will  cut  faces  in  a  vertical 
plane;  and  a  face  mill  (Figs.  129  and  130)  set  on  a  horizontal 
spindle,  will  cut  faces  in  a  vertical  plane.  At  present  we  are  only 
considering  ultimate  results  in  reference  to  truth  and  finish,  and 


Fig.  126. 


Fig.  127. 


not  the  element  of  time,  which  will  sometimes  determine  the 
choice  of  one  method  in  preference  to  another. 

But  when  we  get  away  from  work  of  small  and  moderate 
dimensions,  and  plain  work,  conditions  often  render  one  method 
preferable  to  another.  Thus,  when  large  surfaces  are  in  question, 


MILLING  CUTTERS. 


105 

the  edge  milling  is  generally  preferable  to  face  milling.  Large 
surfaces  are  often  long  as  well  as  wide  ;  and  if  not,  then  it  is  often 
desirable  to  make  up  a  considerable  length  by  arranging  a  number 


of  pieces  in  series,  and  tooling  over  the  lot.  Long  edge  mills 
employed  on  planer  types  of  machines  are,  then,  the  best  to  use, 
because  the  whole  area  can  frequently  be  gone  over  with  a  single 


Fig.  129. 


traverse.  The  mills  may  be  single,  or  the  length  may  be  made 
up  of  two  or  three  narrower  mills  of  the  same  diameter,  preferably 
with  diagonal  teeth  in  opposite  directions  as  in  Fig.  119,  p.  99. 


Fig.  130, 

For  all  gang  milling,  the  horizontal  position  of  the  spindle  is 
best.  The  work  is  held  more  firmly  on  the  table,  and  is 
steadier  than  it  would  be  if  held  otherwise.  A  long  arbor  can  be 
used  more  readily  on  a  horizontal  spindle  than  on  a  vertical  one. 


TOOLS. 


io6 

An  exception  to  the  rule  :that  large  surfaces  are  more  suitably 
tooled  with  horizontal  spindle  machines  and  edge  mills,  occurs  in 
the  case  of  large  face  mills  with  inserted  teeth.  These,  however, 
are  not  employed  so  much  in  the  finer  work  of  the  machine  shop. 
Their  more  special  function  is  the  rough-facing  off  of  the  ends  of 
castings  and  forgings,  and  the  axis  is,  as  a  rule,  horizontal ;  though 
smaller,  face  mills  with  inserted  teeth  are  sometimes  used  on 
vertical  spindles. 

The  great  length  of  the  arbors  of  the  planer  millers  renders 
the  building-up  of  cutters  in  gangs  a  necessity.  There  are  three 
or  four  devices  adopted  in  building-up  gang  mills,  when  it  is 
necessary  to  maintain  a  uniform  breadth  over  extreme  edges, 
compensating  for  the  diminution  of  width  which  naturally  follows 
on  wear  or  regrinding.  The  same  devices  are  serviceable  as  a 
means  simply  of  preventing  a  mark  on  the  work  due  to  the  jointing 
of  the  mills.  One  of  the  earliest  adopted  was  that  of  having  a 
diagonal  joint.  Another  consists  in  making  the  teeth  (Fig.  13 1) 
to  overlap.  But  this  is  only  practicable  when  there  are  teeth  on 
the  ends.  The  simplest  plan  is  to  make  a  shallow  clutch  or  claw 
joint  between  the  ends,  either  slotting  the  mills  right  across,  or 
partially  only  (Figs.  132  and  133).  Both  methods  are  adopted, 
the  former  being  the  simpler.  Either  effectually  prevents  the 
formation  of  a  joint  mark,  and  compen.sation  for  wear  is  effected 
by  the  insertion,  when  necessary,  of  a  sheet  of  paper  or  metal 
between  the  joints.  Fig.  134  illustrates  a  pair  of  mills  arranged 
with  a  plain  distance  piece  between.  They  can  be  used  for 
milling  a  pair  of  grooves,  or  outer  faces,  or  inner  faces  only.  These 
are  employed  for  nut  milling  also.  Fig.  135  illustrates  a  gang  mill 
made  for  a  special  purpose  by  the  Becker-Brainard  Company,  to 
cut  on  eight  faces,  the  section  of  its  work  being  seen  beneath. 
The  outer  faces  are  tooled  by  inserted  tooth  mills.  Provision  is 
made  for  side  adjustment  of  the  mills  a,  a  by  the  screwed  collar 
B,  a  method  used  with  success. 

Although  the  gang-mills  have  a  formidable  appearance,  as 
though  of  necessity  most  costly  tools,  yet  they  are  not  .so  in  fact 
in  shops  where  milling  is  done  extensively.  Given  a  good  stock 
of  cutters  to  select  from,  and  suitable  arbors  and  collars  of  different 
lengths,  almost  any  required  combinations  of  cutters  can  be  built 
up  for  face  and  edge  work,  for  operating  on  several  surfaces  at 
once,  and  on  several  distinct  pieces  at  one  time. 


MILLING  CUTTERS. 


107 


Fig.  131. 


Fig.  135- 


io8 


TOOLS. 


It  is  easy  to  arrange  gangs  of  cutters  to  operate  either  on  dif¬ 
ferent  pieces  of  work,  or  on  different  parts  of  the  same  piece. 
Thus,  several  parallel  grooves  can  be  tooled  with  cutters  arranged 
as  in  Fig.  136,  with  distance  collars  between  them,  the  grooves 
being  tooled  on  edges  and  on  bottom  faces  at  once.  This  is  one 
example  in  which  there  is  no  question  at  all  respecting  the  over¬ 


whelmingly  greater  economy  of  milling  over  planing.  The  larger 
'the  number  of  grooves  the  larger  the  economy. 

Most  of  the  narrow-edge  mills  like  Figs.  126  and  127  are  face 
mills  also,  having  teeth  cut  on  both  faces.  By  this  device  faces 
and  edges  can  be  cut  on  work  simultaneously  as  in  Fig.  136. 
Arranging  as  in  Fig.  137,  a  central  mill  can  be  cutting,  in 


Fig.  137. 


Fig.  138. 


addition  to  the  others.  Fig.  138  is  another  combination.  These 
examples  are  indicative  only  of  the  very  many  combinations  which 
it  is  possible  to  build  up  with  mills  of  different  dimensions  and 
shapes  to  suit  different  classes  of  jobs.  Angular  grooves,  convex 
and  concave  sections,  and  any  irregular  forms  can  be  tooled  alone, 
or  in  combination  with  plane  surfaces,  with  milling  cutters. 


MILLING  CUTTERS. 


Angular  mills  of  various  sections — of  which  Figs.  139,  140,  are 
typical — are  used  for  a  variety  of  purposes,  as  for  grooving  milling 
cutters,  cutting  vees,  &c. 


The  great  breadth  of  surface  which  can  be  tooled  by  a  milling 
cutter,  and  the  fact  that  the  time  required  for  the  return  stroke  of 
the  planer  and  shaper  is  saved  in  milling,  do  not  represent  the 


Fig.  141. 


whole  of  the  important  economies  obtained.  The  greatest  ad¬ 
vantage  often  lies  in  the  fact  that  any  number  of  profiled  forms 
can  be  milled  all  alike,  by  having  these  forms  embodied  in  the 
shapes  of  the  milling  cutters.  In  large  volumes  of  work  this  is 
where  the  milling  machines  score  most  heavily.  It  is  the  case  in 


1  10 


TOOLS. 


some  parts  of  cycle  fittings,  as  pedal  cranks  and  sprocket  wheels, 
the  mills  for  which  are  shown  in  Figs.  141,  142.  Lathe  beds  of 
vee’d  section  and  machine  slides  are  similarly  treated  (Fig.  143). 


A  familiar  example  of  the  value  of  profiled  cutters  is  seen  in  the 
cutting  of  gear  wheels,  which  otherwise  would  have  to  be  planed 
out.  The  teeth  of  racks  are  cut  similarly.  Several  teeth  can  be 

cut  simultaneously  by  arranging 
several  similar  cutters  in  parallel 
series.  The  teeth  of  worm-wheels 
are  cut  with  hobs,  which  are 
really  mills  with  coarse  teeth. 

The  practice  of  some  firms 
is  to  mill  out  the  semicircular 
seats  of  plummer  blocks  and 
divided  bearings  with  a  tool  like 
Fig.  144  in  preference  to  boring 
them.  At  the  same  time,  if  the 
cutter  is  so  profiled,  the  top 
faces  and  the  shoulders  for  the 
cap  are  milled.  This  is  eco¬ 
nomical  in  one  respect.  But 
the  cutters  are  expensive,  and  when  they  wear  their  dimensions 
become  altered.  The  use  of  milling  cutters  in  preference  to 
other  methods  of  tooling  for  any  given  job  must  always  be  decided 
on  its  merits. 

Profile  milling  is  invading  the  wwk  of  the  lathe.  Though  for 
producing  circular  work  of  large  diameter  the  lathe  retains  its  pre¬ 
eminence,  yet  the  milling  machine  is  appropriating  some  sections 


MILLING  CUTTERS. 


Ill 


of  that.  Many  gear-wheel  blanks  are  now  milled  circularly  instead 
of  being  turned,  including  the  blanks  for  spurs,  bevels,  and 
worms.  Profile-cutters  are  so  eminently  adapted  to  this  class  of 
work,  ensuring  that  a  number  of  blanks  will  be  alike,  that  their 
employment  will  increase. 

There  is  practically  little  or  no  choice  of  methods  in  profile 
work,  for  the  milling  machine  takes  it  nearly  all.  It  cannot  be 
done  with  close  precision  by  grinding,  because  the  traversing 
motion  which  is  so  essential  a  feature  in  grinding  is  absent,  and 
without  this  true  grinding  is  not  possible.  If  an  emery  wheel  is 
turned  to  a  profiled  form  it  will  not  retain  its  section  long  enough 
for  very  accurate  work.  It  is  adapted  for  grinding  concave  and 
convex  edges  for  certain  purposes,  but  not  for  mutual  and  exact 
fitting  of  parts.  Thus,  it  is  very  suitable  for  gumming  or  deepen¬ 
ing  the  teeth  of  circular  saws,  for  finishing  the  concavities  of 
bearings  which  are  less  than  hemispherical,  as  in  axle-boxes  and  in 
the  comparatively  rough  bearings  of  trolleys,  and  for  imparting  the 
convex  edges  to  flat-webbed  connecting  rods,  &c.  These  are 
typical  of  a  considerable  volume  of  work  within  which  the  profile 
grinding-wheel  finds  its  proper  sphere.  But  it  does  not  include 
that  larger  range  which  is  almost  wholly  appropriated  by  the  profile 
milling  cutters. 

The  latter  retain  their  shape  unaltered  until  worn  out  by  re¬ 
peated  regrindings,  and  are  accurate  enough  for  the  most  exacting 
requirements  of  the  engineer. 

There  is  no  comparison  between  the  work  of  a  profiled  tool 
and  that  of  separate  cutters  in  planers,  which  would  have  to  be  re¬ 
adjusted  several  times  in  the  classes  of  work  named  above,  and 
which  are  typical  of  many  other  Jobs.  Planing  tee-slots  involves  the 
use  of  both  right  and  left  handed  tools,  and  tools  for  the  bottom 
and  top  edges,  requiring  careful  feeding  by  hand.  Done  by  mill¬ 
ing,  a  cutter  first  roughs  out  the  width  of  the  narrower  slot,  and 
the  tee-shaped  cutter  finishes  at  one  traverse  without  hand  feeding 
at  all.  The  work  of  three  distinct  cuts  on  the  planer,  with  right 
and  left  hand  tools,  is  done  at  one  traverse  of  the  milling  machine. 

Edges  are  profiled  on  both  vertical  and  horizontal  machines. 
The  profiling  pin  in  these  machines  is  tapered,  in  order  to  afford, 
by  means  of  its  vertical  adjustment  against  the  edges  of  the  former, 
of  the  use  of  roughing  and  finishing  cuts,  and  of  adjustment  for 
the  wearing  down  of  cutters.  The  pins  are  held  in  a  boss  in  the 


1 12 


-  TOOLS. 


smaller  machines,  so  that  the  distance  of  their  centres  from  the 
centre  of  the  spindle  is  fixed.  In  the  larger  machines  the  pins 
move  in  slots,  so  that  the  centres  can  be  varied  (Fig.  145).  The 
vertical  adjustments  of  the  pins  are  readily  made,  and  their 
positions  fixed  by  lock  nuts. 

The  former,  or  templet  a,  is  made  of  stout  steel  metal,  pre¬ 
ferably  of  steel  for  durability,  and  is  bolted  to  a  block  on  the  bed, 
so  leaving  the  profile  edges  clear  for  the  pin  to  trace  round.  The 
templet  is  pulled  against  the  pin  b  either  by  the  lever  in  the  small 


machines  or  by  the  weight  in  the  large  ones.  The  vertical  ad¬ 
justment  of  the  slide  is  controlled  by  a  stop,  and  stops  control  the 
horizontal  position  of  the  slide. 

Face  milling  is  a  practice  which  is  adapted  to  an  extremely 
wide  range  of  work.  It  is  more  convenient  in  many  cases,  and 
more  economical  than  edge  milling.  The  cutters  need  not  be 
expensive,  and  there  is  scarcely  a  limit  to  the  size  in  which  they 
can  be  made. 

The  largest  face  mills  have  inserted  teeth  ;  and  the  general 
method  of  insertion  is  to  drill  or  cast  holes  in  a  block  or  head  of 


MILLING  CUTTERS. 


113 

cast  iron,  insert  the  separate  tool  points  or  teeth,  and  pinch  them 
in  place  with  set  screws.  In  some  cutters  the  tool  points  are 
inserted  diagonally  at  an  angle  of  a  few  degrees,  to  impart  some 
desirable  amount  of  front  rake.  The  cutters  are  turned  up  in 
place,  then  removed  and  backed  off,  hardened,  and  replaced. 
That  may  be  called  the  standard  and  the  older  practice.  Of  late 
years  there  have  been  several  variations  therefrom,  the  endeavour 
being  to  avoid  the  work  of  tapping  a  number  of  holes,  and  also  to 


Fig.  146. 


Fig.  147. 


make  a  firmer  job.  Mills  have  been  made  in  which  the  teeth 
have  been  cast  into  the  block,  and  they  are  said  to  have  answered 
well.  In  the  absence  of  experience  of  such  cutters,  one  would 
expect  to  find  the  temper  drawn,  and  to  find  them  working  loose. 

When  teeth  are  inserted  and  secured,  they  may  either  be 
inserted  in  holes  in  the  body,  or  in  slots  in  the  edges  of  the  body. 
It  is  not  necessary  to  set  them  at  an  angle  in  order  to  impart  front 
rake,  though  this  is  often  done.  It  is  simpler  to  fit  them  squarely, 
and  impart  the  front  rake  by  grinding  the  face  of  each  tooth. 

H 


TI4 


TOOLS. 


The  following  examples  are  taken  from  the  practice  of  the 
Becker-Brainard  Company.  Fig,  146  is  a  face  mill,  duplicated. 
It  can  be  used  for  facing  only,  or  for  slotting  a  groove,  or  for 
finishing  the  faces  of  two  separate  pieces  of  work,  brought  up 
against  each  face.  The  tool  points  are  of  circular  section,  and 
are  held  in  position  each  with  a  set  screw. 

Fig.  147  is  an  example  of  a  cutter  in  which  the  tool  points 
are  still  circular,  but  inserted  in  the  edges  of  the  body.  They 
are  secured  by  taper  pins,  fitting  partly  into  the  cutter,  and  partly 
into  the  body.  Or  screws  may  be  used  instead  of  taper  pins. 
The  ends  of  the  tool  points  can  be  used  alone  and  singly,  or 


the  edges  and  ends,  the  combination  being  that  of  the  two  types 
of  mills. 

Fig.  148  is  a  variation  of  Fig.  147,  though  it  fulfils  the  same 
functions.  The  cutters  are  angular  instead  of  circular.  They  fit 
grooves  around  the  body,  and  are  held  in  position  each  with  a 
taper  pin. 

One  of  the  most  common  devices  for  securing  teeth  is  by  the 
insertion  of  pins  midway  between  the  cutters,  as  in  Fig.  149. 
The  cutters  fit  in  their  grooves,  and  the  metal  in  the  body  is 
slotted  midway  between  each  to  permit  of  some  elastic  movement. 
The  insertion  of  a  tapered  pin  in  a  hole  drilled  and  reamered  in 


MILLING  CUTTERS.  115 

the  centre  of  each  slot  opens  the  metal,  and  produces  pressure 
against  the  cutter  flanks  to  right  and  left. 

The  adoption  of  the  practice  of  inserting  tooth  points  into  a 
body  of  cast  iron  is  but  an  extension  of  the  principle  of  tool  points 
in  tool-holders  versus  solid  tools.  The  cost  of  the  steel  alone  for 
large  solid  milling  cutters  is  very  heavy.  Then  there  is  the  expense 
of  producing  the  teeth  on  a  universal  milling  machine,  or  on  a 


Fig,  150. 


special  cutter-forming  machine,  which  is  a  slow  process.  And  after 
the  work  is  done,  the  mill  may  fail  in  the  hardening  through  want 
of  homogeneity  in  the  steel,  or  owing  to  failure  in  carrying 
through  the  operation.  Then  there  is  a  further  risk  of  the  teeth 
becoming  injured  in  working,  being  fractured  or  jagged  from 
causes  inherent  to  the  machine,  or  in  the  hardening,  or  in  the 


nature  of  the  material  which  is  being  operated  on.  So  that  large 
cutters  are  costly  and  troublesome.  Having  cutters  with  inserted 
teeth,  the  very  best  quality  of  steel  can  be  used  for  the  teeth. 
They  need  not  be  expensive  to  make,  or  troublesome  to  temper. 
If  a  tooth  becomes  broken  it  is  easily  replaced.  In  these  respects 
therefore,  the  inserted  tooth  mill  is  the  analogue  of  the  tool  point 
gripped  in  a  tool-holder, 


TOOLS. 


1 16 


The  same  device,  that  of  tool  points,  which  is  carried  out  in 
the  face  mills,  has  been  adopted  in  some  large  axial  mills.  In 

one  type  of  these  the  teeth  are  formed 
in  continuous  strips  of  steel,  instead  of 
as  points  driven  into  drilled  holes.  Fig. 
1 50  shows  a  part  section  of  a  mill  built 
in  two  lengths.  The  strips  a,  a  lie  in 
grooves  planed  diagonally  across  the 
body  (Fig.  15 1),  and  they  bear  wholly 
against  the  grooves  on  one  side  (Fig. 
152),  but  the  greater  portion  of  the  metal 
is  removed  from  the  side  opposite  to 


Fig.  152. 


receive  a  wedge  piece  b.  The  latter  is  held  down  with  screws 
tapped  into  the  cast  body  c,  and  presses  against  adjacent  strips. 


MILLING  CUTTERS. 


117 

The  latter  are  turned  up  in  place,  and  their  faces  milled  radially, 
as  in  solid  mills.  They  are  then  serrated  to  form  single  cutting 
teeth.  The  serrations  are  not  imparted  in  a  helical  curve,  but  in 
parallels,  the  teeth  alternating  (Fig.  15 1).  Each  alternate  set 
is  turned  with  the  others  removed.  There  is,  therefore,  continuous 
cutting  across,  with  the  advantage  of  the  action  of  single-tooth 
points. 

The  large  slabbing  cutter  shown  in  Fig.  153  has  provision  for 
lubricant  being  forced  directly  on  the  cutters,  which  is  effected 
by  distributing  the  oil  from  the  inside,  through  the  hollow  spindle, 
and  thence  to  the  radiating  holes  which  meet,  and  discharge  at 
each  cutter,  through  a  small  hole  underneath.  This  is  a  good 
device  for  ensuring  coolness  of  working  and  thorough  washing 
away  of  chips,  but  the  expense  of  making  would  be  a  deterrent  to 
its  general  use,  while  practically  as  good  results  can  be  secured  by 
an.  ordinary  outside  flow  of  pumped 
lubricant. 

For  rough-cutting  wide  surfaces, 
the  toothed  mills  (Fig.  154),  act 
more  expeditiously,  and  wuth  less 
expenditure  of  power,  than  the  mills 
with  continuous  cutting  edges,  d'he 
reason  is  that  they  operate  in  detail 
on  a  number  of  small  areas  in  rapid 
succession,  so  breaking  up  the  metal  into  chips,  instead  of  re¬ 
moving  it  in  one  long  shaving.  The  principle  of  their  construc¬ 
tion  is  simple,  It  is  as  though  the  teeth  of  an  ordinary  spiral 
mill  were  broken  up  into  a  number  of  separate  teeth  by  cutting  a 
square-threaded  treble  screw  thread  round  the  mill.  The  idea  at 
first  was  deemed  contrary  to  sound  practice,  because  it  was 
thought  that  the  corners  of  the  numerous  short  teeth,  being  un¬ 
supported,  would  become  broken  off  when  cutting.  Experience, 
however,  has  demonstrated  the  fallacy  of  this  idea,  and  these 
toothed  mills  are  used  extensively  in  England  and  have  been 
adopted  in  America,  when  heavy  cutting  has  to  be  done. 

In  the  case  of  cutters  the  sides  of  which  are  curved  or  tapered 
towards  the  circumference,  the  shape  can  be  retained  under  con¬ 
stant  regrinding  by  a  device  first  embodied  in  Messrs  Brown  & 
Sharpe’s  formed  cutters  for  gear  wheel  teeth  and  some  gang  mills. 
It  consists  in  striking  the  centre  of  backing  off  from  a  point  b, 


ii8 


^  TOOLS. 


other  than  the  centre  a,  as  shown  in  Fig.  155.  The  thickness  of 
the  teeth  remains  constant,  however  much  the  faces  are  ground 

away,  provided  the  faces 
are  always  ground  radially. 
Mills  of  similar  type  are 
made  for  cutting  thegrooves 
in  drills,  reamers,  and  taps. 

The  lubrication  of  mill¬ 
ing  cutters  is  a  necessity, 
cast  iron  being  the  excep¬ 
tion.  The  heavier  the 
cutting  done,  the  greater 
the  heat  generated,  with 
the  consequences  of  injur¬ 
ing  the  cutting  edges,  and 
causing  expansion  of  the 
cutters  and  of  the  work, 
and  lessening  the  duty 
obtained.  In  the  best 
practice  there  is  no  stint 
of  lubricant,  and  as  the  oil  is  separated  and  used  again,  the 
cost  is  slight.  The  larger  the  cutters,  the  greater  the  need  of 
ample  lubrication,  the  oil  being  sprayed  over  from  a  pipe.  A 


Fig.  155. 


practice  has  been  introduced,  therefore,  of  lubricating  from  within, 
after  the  same  principle  adopted  in  drills.  The  Newton  Machine 
Tool  Works  have  a  patent  method  of  lubricating  their  slabbing 
cutters,  shown  in  Fig.  156.  a  is  the  arbor,  pierced  with  a  hole 
for  the  lubricant,  which  comes  in  through  the  pipe  u.  c  is  the 


MILLING  CUTTERS. 


ii9 

cutter,  hollowed  to  form  an  oil  chamber.  The  lubricant  flows 
through  radial  holes  in  the  cutter  body  to  the  teeth.  The  teeth 
of  these  cutters,  like  those  of  the  Ingersoll,  are  staggered  to 
break  up  the  chips. 

Oil  or  soapy  water  is  used  generally  for  the  lubrication  of 
milled  work  in  all  metal  except  cast  iron  and  brass.  For  occa¬ 
sional  jobs,  oil  is  often  dispensed  with;  but  where  milling  is 
practised  as  a  system,  it  is  employed  in  quantity.  Then  it  is 
used  far  in  excess  of  what  would  be  required  for  lubrication 
simply,  the  work  being  flooded  with  it.  The  oil  facilitates  the 
formation  of  a  smooth  surface,  and  dislodges  and  swills  the 
cuttings  away.  To  the  most  complete  machines  an  oil-pump  and 
tank  is  affixed,  by  which  an  ample  supply  with  little  waste  is 
secured. 

Rough  castings  and  forgings  do  comparatively  little  damage  to 
single-cutting  tools,  but  they  injure  the  edges  of  milling  cutters. 
Moreover,  the  milling  of  large  surfaces  is  usually  costly  by  reason 
of  the  first  expense  and  maintenance  of  cutters,  unless  large 
numbers  of  similar  pieces  are  to  be  operated  on. 

Since  milling  cutters  are  tools  costly  to  make,  and  to  keep  in 
order,  and  since  their  efficiency  depends  on  their  truth,  and  on 
the  keenness  of  their  edges,  it  follows  that  it  is  not  well  to  distress 
those  edges  except  by  legitimate  duty.  As  metal  which  is  non- 
homogeneous,  and  the  scale  of  castings  and  forgings  are  very 
destructive  to  the  keen  edges  or  the  cutters,  in  shops  where  a 
good  system  prevails,  therefore,  hard  castings  are  annealed,  and 
scale  is  removed  by  pickling,  or  by  grinding. 


CHAPTER  XL 


Boring  Tools  for  Wood. 


The  Bradawl — The  Performance  of  the  Gimlet  Type — Its  Drawbacks — Bits, 
and  Augers — Centre-Bit — Its  Unbalanced  Action — Expanding  Centre-Bit 
— American  Screw  Bits — Forms  of  their  Cutters — Their  Advantages — 
Counterboring — Improved  Braces. 


The  bradawl  stands  alone  among  boring  tools.  It  forms  its 
hole  by  a  simple  thrusting  aside  of  the  wood  fibres.  If, 
however,  it  is  being  thrust  near  the  edge  or  end  of  a 
piece  of  stuff,  the  chisel  edge  should  be  set  across  the  grain  to 
sever  it*  Even  the  humble  bradawl  has  clearance  like  a  twist 
drill  in  the  longitudinal  direction,  being  smaller 
in  diameter  at  the  handle  end  than  at  the 
cutting  edge. 

All  boring  tools  for  wood,  the  bradawls  and 
centre-bits  excepted,  are  magnified  gimlets,  of 
the  shell  or  of  the  twist  type  (Figs.  157  and 
158).  The  two  essentials  in  the  formation  of 
these  little  tools  are  the  getting  into  the  wood, 
and  clearing  the  cuttings  out.  The  screw  at  the 
end  of  each  worms  its  way  in,  with,  or  without 
slight  pressure ;  the  entrance  of  the  shell  in  the 
one,  or  of  the  twist  in  the  other,  cuts  the  fibres, 
which  then  creep  up  the  hollow  part  of  the  shell. 
Fig.  157*  Fig.  158.  or  up  the  twist,  and  so  out  of  the  hole — that  is, 
they  ought  to  do  so ;  but  it  is  in  so  imperfect 
a  fashion  that  in  deep  holes  in  hard  wood  the  gimlet  has  to  be 
withdrawn  once  or  twice,  in  order  to  get  the  cuttings  out,  or 
else  considerably  more  pressure  must  be  exercised  as  the  hole 
deepens,  and  the  friction  increases.  In  hard  wood  the  gimlet  thus 
gets  hot,  and  in  larger  sizes  it  has  to  be  cooled  by  dipping  it  in 
tallow  from  time  to  time. 


BORING  TOOLS  FOR  WOOD. 


I2I 


u 

u 

Fig.  159. 


a 


Fig.  160, 


Fig.  161. 


Nor  are  these  the  only  drawbacks.  Another  lies  in  the  fact 
that,  as  there  is  no  provision  made  in  these  tools  for  nicking  a 
circle  round  the  hole  to  be  bored, 
they  cannot  be  depended  on, 
either  to  bore  holes  true  to 
centre,  or  round  and  smooth. 

This  matters  little  in  the  gimlets, 
which  are  used  mostly  for  the 
insertion  of  screws ;  but  it  does 
matter  when  bigger  tools  are 
built  on  patterns  much  resem¬ 
bling  them.  Such  tools  are  the 
spoon,  shell,  and  nose  bits 
(Figs.  159,  160,  and  161),  and 
the  half-twist  bits.  Of  these, 

only  the  last  named  is  capable  of  centring  exactly;  the  spoon 
bits,  and  shell  bits  will  only  do  so  approximately,  and  the 
nose  bit  not  at  all.  But  the  latter,  once  entered,  tends  to  draw 
itself  into  the  hole,  and  its  withdrawal  brings  out  the  core  by  the 
lip  or  nose,  a,  and  this  therefore  is  a  favourite  form  for  making 
non-thoroughfare  holes. 

A  shell  auger  (Fig.  162)  is  a  magnified  nose  bit,  but  on  ac¬ 
count  of  its  much  larger  ^iameter,  the  drawbacks  of  this  form 
become  most  evident.  In  the  first  place,  a  shell 
auger  will  not  start  a  hole  neatly ;  hence  a  centre-bit 
or  a  gouge  is  generally  used  to  commence  with. 
The  slope  of  the  auger  lip  tends  to  draw  the  instru¬ 
ment  into  the  hole  under  slight  pressure,  or  often 
with  no  pressure  at  all.  But  the  tool  must  be  with¬ 
drawn  from  time  to  time  in  a  deep  hole  in  order  to 
get  out  the  core,  and  it  also  becomes  hot,  and  has  to 
be  dipped  in  tallow.  In  hard  wood,  or  in  end  grain, 
boring  with  an  auger  is  hard  work. 

A  drawback  in  all  tools  of  the  class  just  named  is 
the  absence  of  a  nicking  edge  to  precede  the  longi¬ 
tudinal  cutting  edges.  The  latter  have  both  to  cut 
the  circle,  and  clear  the  hole.  But  the  leading  corner, 
which  is  not  a  good  cutting  edge,  has  to  do  the 
circular  cutting.  Such  tools  are  therefore  unsuitable  for  boring 
holes  true  and  clean,  and  they  are  rough  and  inaccurate  instru- 


Fig.  162. 


122 


TOOLS. 


merits  for  deep  holes.  Hence  the  centre-bit  (Fig.  163)  takes 
their  place  for  the  first-named  kind  of  work,  where  exact  centring 

is  necessary,  and  where  smoothness  of 
edge  is  required. 

And  yet  the  centre-bit  is  far  from 
fulfilling  these  requirements  in  a 
decent  manner.  In  its  ordinary  form 
it  has  no  screw  to  start  it  truly,  but  a 
triangular  tit  instead ;  the  nicker  is 
single,  and  therefore  unbalanced,  and 
the  cutter  is  single  too.  In  small  bits 
these  unbalanced  forces  matter  little, 
but  when  f  in.  or  i  in.  diameter  is 
exceeded,  then,  especially  when  boring 
in  hard  wood,  the  bit  turns  jerkily,  and 
-penetrates  slowly.  There  is  nothing  to 
help  to  draw  the  bit  into  its  work  save  the  cutter,  and  that  being 
unbalanced,  is  as  liable  to  dig  in  and  hitch  as  to  cut  sweetly  and 
smoothly.  And  further,  there  is  no  provision  for  guidance  in  the 
short  body  of  the  bit  as  there  is  in  an  auger,  or  a  nose  bit,  or  a 
shell  bit,  or  a  gimlet,  or  a  twist  drill.  The  only  control  exercised 
is  that  of  the  workman,  who  judges  by  the  eye  whether  he  is 
driving  the  hole  plumb,  or  he  gets  a  mate  to  take  a  sight,  and  tell 
him  which  way  to  lean  the  brace  over. 

Another  drawback  to  the  centre-bit  is  that  it  never  bores  to 
its  normal  diameter,  but  always  larger — g\-,  or 

more,  according  to  its  size.  Another  is  that  it  is 
only  suitable  for  boring  plank  way  of  the  grain.  In 
end  grain,  and  diagonally  it  works  with  difficulty, 
and  cannot  be  depended  on  to  produce  so  straight 
and  true  a  hole  as  in  the  plank  way.  In  fact,  in 
open,  spongy,  soft  wood  it  is  practically  impossible 
to  bore  holes  in  end,  or  cross  grain  with  this  instru¬ 
ment.  The  screw  centre-bit  (Fig.  164),  is  but  little 
better.  The  screw  is  better  than  the  triangular 
centre-tit  of  Fig.  163,  but  the  other  drawbacks 
remain. 

English  woodworkers  have  to  thank  American 
invention  for  producing  some  of  the  improved  forms  of  boring  tools. 
The  expanding  centre-bit  is  a  great  deal  better  than  the  common  bit, 


Fig.  164. 


BORING  TOOLS  FOR  WOOD. 


123 


not  only  by  reason  of  its  extensibility  to  suit  holes  of  different  sizes, 
and  the  exact  size  of  holes  to  which  it  can  be  set  to  bore,  but 
also  because  it  centres  itself  exactly  by  a  tapered  screw, 
and  the  chip  is  broken  up  by  a  secondary  nicker  nearer 
the  centre  than  the  nicker  which  determines  the  diameter 
of  the  hole,  thus  reducing  the  labour  of  cutting.  The 
shank  of  this  bit  is  also  divided  into  inches  and  quarter 
inches,  so  that  the  depths  of  holes  being  bored  can  be 
readily  seen  at  a  glance.  None  of  the  old  bits  contained 
even  this  provision,  but  bushes  of  various  lengths,  slid  on 
the  shanks,  determine  depths  without  measurement. 

But  generally  speaking,  an  expanding  bit  is  not  so  valu¬ 
able  a  tool  as  sets  of  solid  ones  in  fixed  standard  sizes, 
and  in  the  last  named,  the  difference  in  the  old  and  the 
new'  designs  is  most  apparent. 

The  value  of  these  solid  bits  lies  in  the  fact  that  they 
enter  their  holes  by  accurately  tapered  screws,  so  en¬ 
suring  exact  centring;  that  they  mostly  have  two  nickers, 
and  invariably  two  cutters,  on  opposite  sides  ;  that  they 
have  twisted  clearance  spaces  of  very  large  area,  and 
generally  of  quick  pitch,  for  the  cuttings ;  and 
that  they  run  parallel  back  from  the  cutting 
end  for  the  greater  portion  of  their  length. 

They  thus  fulfil  all  the  conditions  which  an  ideal  boring 
tool  should  do. 

There  are  several  bits  now  sold  which  fulfil  these  re¬ 
quirements  in  greater  or  less  degree.  They  differ  in  the 
shapes  of  their  lips,  in  the  method  of  forming  the  twist, 
and  in  the  amount  of  clearance  left  in  the  twists.  Some 
have  twists  like  those  of  the  old-fashioned  twist  drills,  and 
twisted  augers  ;  others  resemble  the  turns  of  a  screw- 
blade  round  a  stem,  a  form  which  gives  more  clearance 
space  than  the  other  does. 

Fig.  165  is  an  example  of  one  kind — the  Jennings 
with  a  central  screw,  two  nickers,  and  two  cutting  lips. 
This  tool  will  bore  with  about  equal  facility  in  any 


Fig.  165. 


Fi  ^  i66-  direction  of  the  grain,  perfectly  straight  after  it  is  fairly 
^  entered,  and  with  very  slight  exertion  on  the  part  of  the 
workman.  Fig.  166— the  Irwin  bit— differs  from  it  only  in  the 
form  of  the  twist ;  the  screw,  nickers,  and  cutters  being  of  similar 


T24 


TOOLS. 


shapes.  The  cylindrical  shaft,  and  the  screw-like  blade  that  form 
the  spiral  appear  to  give  greater  freedom  of  exit  to  the  cuttings. 
Both,  however,  are  very  perfect  tools. 

In  what  are  termed  auger  bits,  and  in  the  augers  of  this  type 
the  lips  are  usually  turned  up  to  help  in  getting  out  the  chips  (Fig. 
167),  and  they  smooth  the  hole  partly  made.  There  is  the  screw, 
and  two  cutters  still  giving  balanced  forces,  and  as  these  cut 
cleanly  and  sweetly,  the  wood  is  not  torn  by  the  absence  of  nickers. 
In  some  types  the  cutters  are  duplicated  downwards  and  upwards. 
The  ship  auger  (Fig.  168),  is  a  very  old  form,  which  cuts  at  one 
side  and  bottom,  and  has  a  lip  for  withdrawing  the  core ;  some  of 
these  have  a  tapered  screw,  others  are  without  the  screw.  In 
other  bits,  as  the  Irwin  (Fig.  169)  and  the  Gilpin  or  Gedge  (Fig. 


Fig.  167. 


Fig.  170. 


170),  the  cutters  are  gouge-like  in  form,  and  these  cut  very 
sweetly,  while  the  truth  in  the  hole  is  ensured  by  the  screw,  and 
the  prolongation  of  the  cutters  upwards  into  lips. 

Sharpening  of  these  tools  has  to  be  done  occasionally,  as  in 
the  case  of  other  kinds.  But  they  can  soon  be  damaged,  and 
even  utterly  spoiled,  by  injudicious  methods.  The  screws  seldom 
require  touching  up,  unless  the  points  become  broken  off.  If  they 
do,  a  fine  three-cornered  file,  as  used  for  dovetail  saws,  is  the 
proper  one  to  employ.  The  shell  of  a  gimlet  or  of  a  shell  auger 
must  not  be  filed  on  the  outside,  but  in  the  hollow  at  a  (Figs.  157 
and  162).  If  sharpened  on  the  outside  they  would  soon  be 
spoiled  for  cutting,  because  the  edge  would  fall  inside  the  circle 
of  the  diameter.  Nicker  and  cutter  must  also  be  sharpened  on  the 
inside,  as  at  a,  b  in  Fig.  163,  a,  a  \n  Figs.  165  and  166,  and  on 


BORING  TOOLS  FOR  WOOD. 


125 


the  inside  of  the  lips  in  all  cases.  'I'his  preserves  the  diameter  of 
the  nickers  unaltered,  and  prolongs  the  life  ot  the  cutters.  If 
damaged  by  a  nail  there  is  no  help  for  it  but  to  file  back,  and 
take  out  the  notch.  Sweeter  cutting  results  if  the  edges  are 
finished  with  a  small  gouge  slip,  with  which  also  the  burr  can  be 
turned  back. 

These  improved  forms  save  a  vast  expenditure  of  muscle  and 
time,  to  say  nothing  of  the  better  results  that  are  obtained.  And 
here,  too,  as  in  so  many  other  matters,  specialisation  leads  the 
way.  First,  the  manufacture  of  these  tools  lies  in  the  hands  of 
but  a  few  firms.  Second,  the  broad  type  is  modified  to  an  ex¬ 
tent  that  w'as  never  dreamed  of  in  the  old  days  ;  for  different 
craftsmen  may  be  accommodated  with  special  bits  and  augers 
varying  in  length,  in  twist,  in  shape  of  lips,  and  tang  to  suit  their 
exact  requirements.  Moreover,  the  portable  boring  machine,  which 
came  in  several  years  ago,  designed  for  operating  these  auger 
bits,  is,  though  simple,  one  of  the  most  valuable  woodworker  s 
tools  ever  introduced.  Instead  of  using  the  common  brace,  or 
operating  the  cross  handle  turned  by  hand,  in  gimlet  fashion,  it 
substitutes  the  crank  handles  and  mitre  wheels,  giving  power  and 
speed  in  combination,  so  that  it  is  but  the  work  of  a  few  seconds 
to  bore  through  a  foot  of  timber.  And  there  is  the  certainty  that 
the  hole  will  be  plumb,  or  to  the  exact  angle  to  which  the  auger 
is  set.  In  addition,  too,  there  are  the  rapid  adjustments  of  the 
machine. 

The  advent  of  these  boring  tools,  both  accurate,  and  rapid  in 
action,  has  knocked  out  many  of  the  old  ones  in  shop  equipments 
and  men’s  kits.  The  centre-bits  are  common ;  but  where  they 
are  retained,  men  generally  have  a  set  also  of  the  superior  kinds. 
The  shell-lip  augers  are  much  scarcer  than  they  were,  the  screw 
augers  having  largely  taken  their  place.  The  price  of  the  better 
tools,  however,  makes  a  man  cautious  how  he  uses  them.  They 
are  suitable  for  new,  clean  timber  ;  but  in  repairs,  where  nails 
may  lie  hidden  to  trap  the  unwary,  the  old  cheaper  tools  are  used, 
rather  than  risk  injury  to  the  lips  of  the  expensive  screw  bits. 

Every  one  knows  the  trouble  of  counterboring  in  wood.  You 
have,  say,  a  5  in.  hole,  and  want  to  bore  a  |  in.  one  down  to  a 
certain  depth.  The  safe  way  is  to  bore  the  larger  first  and  the 
smaller  afterwards.  But  then  that  is  not  always  practicable  nor 
convenient.  But  a  centre-bit  cannot  hold  in  a  hole  5  in.  in 


126 


TOOLS. 


diameter,  and  so  it  must  be  plugged  temporarily  to  afford  a  centre 
for  the  larger  bit.  An  American  firm  supplies  little  discs  of  soft 

metal  to  fill  small  holes  of  various  sizes 
to  take  the  screw  of  the  large  bit  while 
boring  (Fig.  171). 

Along  with  these  good  tools  better 
braces  are  available.  The  trouble  with 
the  old  braces  was  manifold.  A  hole 
could  not  be  bored  in  a  corner  where 
there  was  no  room  to  turn  the  brace 
round,  nor  at  an  angle  in  a  confined 
position.  Bits  from  different  makers  did  not  fit  alike.  Friction 
was  excessive.  Now  we  have  braces  that  have  ratchet  devices,  so 
that  a  portion  of  a  turn  only  is  required  to  turn  the  bit,  angular 
braces  for  boring  at  an  angle,  ball  races  to  lessen  friction ;  and 
loose  jaws  or  chucks  that  accommodate  themselves  to  tangs  that 
vary  in  angle.  Braces  are  shown  in  Fig.  256,  p.  173. 


CHAPTER  XII. 

Boring  Tools  for  Metal. 

The  Drill — Variations  in  Flat  Drills— Characteristics— Angles— Grinding—  ’ 
Twist  Drills— Early  Forms— Increase  Twist— Constant  ditto— Cutting 
Angles— Clearances— Effects  of  Grinding— the  Point— Speed  of  Drills— 
Conditions  which  Affect  Speed— Lubrication— Oil  Tubes— Shanks — 
Enlargement  of  Holes — Reamers — Boring  Tools — Pin  Drill  or  Counter - 
bore. 

The  drill  is  one  of  the  most  curious  among  tools,  its  re¬ 
markable  feature  being  the  extremely  wide  range  of  forms 
in  which  it  exists.  The  first  drills  were  co-existent  with 
Neolithic  celts;  the  latest  are  still  being  improved  on  their 
immediate  predecessors.  None  of  the  early  drills  could  be  ranked 
with  true  cutting  tools  ;  the  later  types  are  as  truly  so  as  are 
the  chisels  for  wood  and  metal. 

Consider  for  a  moment  the  range  of  variation  in  drills.  All 
must  have  some  clearance,  which  will  vary  from  half  a  degree  to 


Fig.  172. 


ten  degrees  or  more.  All  twist  drills  have  front  rake,  imparted 
by  the  angle  of  the  twist  in  relation  to  the  axis  of  the  drill.  But 
all  straight-fluted  drills  (like  Fig.  172),  which  do  good  work  in 
brass,  have  no  such  angle,  while  the  common  flat  drill  (Fig.  173) 
has  slight  negative  angle.  Then,  in  reference  to  guidance,  there 
is  a  great  difference  between  the  flat  drill  and  the  solid  twist  type. 
The  getting  out  of  the  chips,  which  are  crowded  in  the  case  of 
the  flat  drill,  is  neatly  effected  by  the  grooves  of  the  twist  drill. 

The  old  flat  drills  did  good  work,  as  they  do  now  in  many 
shops,  where  they  are  retained  for  small  work.  They  do  it  in 


128 


TOOLS. 


defiance  of  theoretical  principles  of  tool  formation.  Cutting 
angles  they  have  none,  being  scraping  tools  purely.  The  cutting- 
faces  are  flat,  and  nearly  perpendicular  to  the  faces  being 
bored,  so  there  is  no  front  rake,  or  cutting  angle.  Generally, 
in  fact,  the  cutting  faces  are  ground  off  tapered,  until  the  angle 
becomes  greater  than  90°.  But  they  do  their  work  well,  for 
two  reasons.  The  point  is  narrowed  down,  and  the  edge  is  well 
backed  off,  and  where  their  action  is  nicely  balanced  on  each  side 
of  the  centre,  these  make  up  a  set  of  favourable  conditions  that 

largely  compensate  for  the  one 
defect  of  a  non-cutting  front 
angle.  These  tools  are  not  to 
be  despised  now  in  the  drilling 
of  powdery  cast  iron.  Tough 
wrought  iron  and  steel  are  the 
materials  in  which  they  operate 
least  favourably,  and  only  by 
large  applications  of  oil  will  they 
do  even  a  fair  amount  of  work  in 
these  materials,  without  heating. 

Because  the  common  drill  is 
destitute  of  top  rake  it  is  liable 
to  become  heated  when  fed  too 
hard.  For  this  reason  hand 
feeding  is  best  for  drilling 
machines,  the  skilled  workman’s 
sense  of  touch,  and  sound  being 
the  best  safeguard.  Especially 
— and  this  applies  to  other  kinds 
of  drills — it  should  not  be  forced 
to  its  work  at  the  commencement. 
It  ought  to  be  fed  lightly  at  first,  until  the  hole  is  fairly  entered, 
and  then  a  heavier  feed  may  be  put  on  for  the  completion  of  the 
drilling.  Too  heavy  feeding  causes  a  drill  to  spring,  and  run  out 
of  truth.  It  is  easy  to  drill  holes  accurately  with  the  flat  drill. 
It  is  also  very  easy  to  drill  them  badly. 

It  might  seem  at  first  sight  as  if  the  most  important  points  of 
design  about  the  drill  were  the  angles  a,  Fig.  173,  which  the 
cutting  edges  make  with  the  centre  or  axis,  and  the  angles 
which  they  make  with  the  faces  of  the  drill.  But  measure  a 


Jt' 


Fig-  173- 


BORING  TOOLS  FOR  METAL. 


129 

number  of  drills  taken  at  random  from  a  machine,  or  drawer, 
and  the  difference  in  the  first  will  amount  to  perhaps  8°  or  10° 
n  those  considered  quite  efficient,  and  doing 
good  work.  The  angles  a  therefore  need  not 
be  very  precise.  In  fact,  for  working  on  thin 
plates  of  sheet  iron  and  brass,  the  angle  must 
needs  be  very  obtuse,  like  Fig.  174,  otherwise 
the  point  of  the  tool  would  be  through  the 
sheet  almost  directly,  and  the  drill  wobble,  long 
before  the  effective  diameter  began  to  operate. 

Hence  the  angle  a  will  vary  in  different  drills  Fig.  174. 
between  that  shown  in  Figs.  173  and  174. 

Of  more  importance  is  the  angle  b.  It  should  not  be  very 
acute.  It  need  not  exceed  5°  or  6°  for  iron  and  steel,  though  for 
brass-work  it  is  often  made  as  much  as  10°  or  12”.  If  the  angle 
is  too  great,  the  drill  chatters,  and  loses  its  edge  more  quickly 
than  if  kept  within  the  limits  named  above.  So  that  a  difference 
of  angle  can  be  made  with  advantage  in  drills  intended  for  differ¬ 
ent  metals  and  alloys — less  for  the  harder,  tougher  metals,  greater 
for  the  softer,  more  crystalline  materials.  This  angle  b  is  called 
the  angle  of  relief,  or  the  “clearance”  angle,  its  only  function 
being  to  avoid  friction  between  the  portion  immediately  behind 
the  cutting  edges  and  the  faces  of  the  work  being  cut.  While 
too  acute  an  angle  will  result  in  rapid  wear  of  the  cutting  edges, 
one  too  obtuse,  while  preserving  strength,  and  durability  of  edge, 
will  be  productive  of  great  friction. 

Though  some  considerable  variation  is  permissible  in  these 
matters,  there  is  one  detail  which  admits  of  no  variation  at  all — 
the  symmetry  of  the  edges  c  about  the  axial  centre  a.  Whatever 
the  angles  given  to  the  cutting  parts,  the  bevel  of  the  edges  must 
be  exactly  equal  about  the  centre  a,  both  in  respect  of  radius,  and 
of  slope.  In  a  drill  of  this  kind  the  two  cutting  edges  should 
each  be  doing  an  equal  amount  of  work,  and  the  stress  due  to 
drilling  be  divided  quite  equally  between  the  two.  This  cannot 
be  the  case  when  the  edges  are  unsymmetrical,  which  inevitably 
results  in  loss  of  efficiency,  and  sacrifice  of  good  results. 

In  a  drill  ground  unsymmetrically.  Fig.  175,  the  radius  a 
will  regulate  the  diameter  of  the  drilled  hole,  and  not  the  diameter 
B,  and  the  stress  of  cutting  will  be  thrown  wholly  on  the  side  a, 
and  not  on  b.  Or,  if  one  edge  is  ground  to  a  different  angle 


I 


130 


TOOLS. 


from  the  other,  then  the; stress  of  cutting  is  thrown  wholly  on 
the  edge  with  the  larger  radius,  and  the  hole  will  run  out  of 
centre. 

The  departure  from  accuracy  need  not  be 
great  to  produce  these  results.  The  exaggerated 
amount  shown  in  the  figure  would  not  occur 
in  practice.  A  departure  from  symmetry  which 
could  not  be  detected  by  the  eye  is  sufficient 
to  impair  the  efficiency  of  a  drill. 

If  a  drill  makes  too  revolutions  per  inch  of 
feed,  that  means  that  for  each  revolution  y-^th 
of  an  inch  of  metal  is  cut  away.  If,  therefore, 
there  is  a  want  of  symmetry  only  to  the  extent 
of  Y^th  of  an  inch,  the  whole  of  the  cutting 
will  be  thrown  on  the  side  with  the  larger 
radius. 

A  drill  shaped  unsym metrically  will  not 
make  a  hole  parallel,  but  will  drill  it  tapered, 
the  diameter  being  larger  at  the  bottom  than  at  the  top.  In  fact, 
in  some  special  jobs  holes  are  drilled  thus  purposely,  with  a  drill 
ground  lopsided.  No  matter  how  rigid  the  shank  of  the  drill,  it 
will  infallibly  be  pulled  out  of  perpendicular  by  its  malformation, 
and  the  slighter  the  shank,  the  more  inaccurate  will  be  the  hole. 

When  drills  run  out,  and  cause  holes  to  become  located  out 
of  truth,  which  will  happen  sometimes  even  when  the  drill  is 
correctly  formed,  due  to  carelessness  in  commencing 
the  hole,  or  to  the  presence  of  soft  or  broken  metal, 
then  it  must  be  corrected  before  the  drill  has  pene¬ 
trated  far.  This  is  done  with  a  fitter’s  round-nose 
chisel.  That  side  of  the  hole  from  which  more 
material  should  be  removed  is  chipped  away,  so  that 
the  drill  shall  commence  again  accurately. 

The  application  of  rake  to  the  front  edges  of  the 
flat  drill.  Fig.  176,  was  a  good  idea,  because  by  it  a 
true  cutting  angle  is  obtained.  But  it  gives  a  deal 
of  trouble  in  practice,  because  the  rake  is  soon  lost 
by  regrinding,  and  then  re-forging  and  re-tempering 
become  necessary,  and  so  it  seems  better  to  get  along  with 
the  non-cutting  type. 

The  idea  of  the  twist  drill,  simple  though  it  now  seems,  passed 


BORING  TOOLS  FOR  METAL. 


131 

through  a  period  of  evolution  before  the  modern  drills  were 
developed.  The  original  idea  appears  to  have  been  the  twisting 
by  the  smith  of  a  flat  bar  of  steel  of  rectangular  section, 
so  giving,  in  regard  to  its  method  of  formation,  as  well 
as  ultimate  shape,  a  real  twist.  Years  ago  there  were 
plenty  of  these  (Fig.  177),  to  be  seen  in  engineers’  shops, 
along  with  the  flat  lip  drills.  They  embodied  an  idea 
which  has  been  since  brought  to  perfection,  but  they 
never  supplanted  the  flat  drills,  They  did  not  remove 
good  cuttings  like  the  modern  twist  drills,  but  broke 
them  up,  choking  the  hole.  But,  with  few  exceptions, 
the  type  has  disappeared  before  the  solid  twist  drill, 
although  it  is  still  preserved  in  the  twist  bits  used  for 
wood  boring,  which  do  excellent  work.  The  weakness 
of  this  drill  for  metal-work  lies  in  its  excessive  elas¬ 
ticity  in  small  sizes,  and  therefore  it  does  not  fulfil 
the  conditions  of  hard  work  so  well  as  the  solid  twist  Fig.  177. 
drill  does. 

Somewhere  about  i860.  Sir  Joseph  Whitworth,  and  Mr 
Greenwood  both  made  twist  drills.  Later,  the  Manhattan  Fire¬ 
arms  Company  in  America  started  their  manufacture.  The  first 
drills  failed  because  the  cutting  angles  were  too  keen.  Then  Mr 
Morse  followed,  and  by  reducing  the  cutting  angle  very  much, 
produced  tools  capable  of  doing  good  work.  He  also  devised 
the  grinding  line,  and  the  increasing  twist. 

The  lips  of  twist  drills  are  formed  with  true  cutting  angles, 
and  in  consequence  of  the  circular  form  they  are  not  so  liable  as 
the  flat  ones  to  run  in  their  holes,  nor  bore  larger  than  their  own 
diameter ;  consequently  the  performances  of  these  drills  in  respect 
of  accuracy,  and  also  of  rapidity  of  work  is  in  excess  of  that  of 
common  flat  drills.  Feeds  may  be  increased  100  per  cent,  or 
more  over  those  of  flat  drills  ;  holes  can  be  drilled  so  accurately 
that  the  drills  will  not  afterwards  fall  out  of  the  holes  by  their 
own  gravity.  Another  advantage,  too,  is  that  the  truth  of  a 
hole  is  more  readily  seen  by  using  a  twist  drill.  Before  it  has 
penetrated  far,  the  fit  of  the  drill  in  its  hole  indicates  this. 

For  many  years  past  two  kinds  of  twist  drills  have  been  made 
— the  Morse,  with  an  increasing  twist  (Fig.  178)  and  grinding 
line ;  and  those  made  with  a  regular  twist,  and  without  a  grinding 
line.  In  the  former,  the  cutting  angle  becomes  more  obtuse  as 


132 


TOOLS. 


the  drill  wears  down ;  in  the  latter  it  remains  constant.  In  the 
former,  the  grinding  line  is  used  as  an  aid  to  symmetrical  grind¬ 
ing;  in  the  latter  this  depends  wholly  on  the  guidance 
of  the  grinding  machine  used,  or  on  the  gauging 
following  hand  grinding.  Now,  these  cannot  be  both 
better,  yet  each  claims  supposed  advantages  over  the 
other.  It  is  rather  remarkable  that  the  question  of 
,  constant  twist  versus  increase  twist  in  drills  should  still 
be  an  open  one.  The  English-made  drills  are  mostly 
of  the  first,  the  American  of  the  second,  class.  In 
actual  work  there  seems  little  to  choose  between  the 
two.  The  points  in  favour  of  each  are  the  following : — 
In  favour  of  the  increase-twist  type  it  is  said  that 
the  chips  get  away  more  readily  as  the  twist  straightens 
out  towards  the  shank  end  than  they  do  from  a  con¬ 
stant  angle  drill.  Against  this,  even  if  the  statement 
^  is  correct,  is  set  the  fact  that  as  the  drill  wears  back, 
'  the  cutting  angle  becomes  more  obtuse,  changing 
from  the  original  angle  to  one  of  about  io°  less  when 
worn  to  a  stump,  and  leaving  the  middle  portion  of 
the  drill  thicker. 

The  gradual  thickening-up  of  the  web  of  the  drill 
from  the  point  to  the  shank,  which  is  done  to  render 
it  stronger  to  resist  torsional  strains  than  one  having 
a  web  of  parallel  thickness  would  be,  is  unfavourable 
Fig.  178.  to  delivery  of  chips.  In  regard  to  the  alteration  in 
angle,  it  is  well  to  remember  that  worn  drills  are 
well  suited  for  drilling  hard  steel  and  brass,  while  they  can  be 
utilised,  by  re-grinding,  for  drilling  slots  and  keyways.  Further,  by 
the  time  a  drill  wears  nearly  to  a  stump,  it  has  well  paid  for  itself. 

Since  in  the  constant-twist  type  the  cutting  angle  remains  un¬ 
changed,  the  makers  of  this  type  lay  great  emphasis  on  the 
constancy  of  the  cutting  angle  during  the  life  of  the  drill.  There 
would  be  something  in  the  argument  if  all  metals  and  alloys 
demanded  a  constant  angle.  But  as  they  do  not,  the  supposed 
advantage  seems  to  have  been  overrated.  The  angle  of  with 
the  axis  is  a  good  mean,  and  that  is  a  general  one  with  twist  drills 
when  new.  But  a  few  degrees  more  is  certainly  not  detrimental 
to  good  work,  while  in  some  cases  it  would  be  preferable  to  the 
lesser  angle. 


BORING  TOOLS  FOR  METAL. 


133 


In  the  solid  twist  drills  there  are  other  points  of  variation. 
One  of  the  curious  facts  is,  that  until  within  the  last  few  years 
no  attempt  has  been  made  to  produce  twist 
drills  with  different  cutting  angles  to  suit 
different  kinds  of  metals — another  proof 
that  the  maintenance  of  very  exact  distinct 
cutting  angles  for  different  metals  operated 
upon,  need  not  be  insisted  upon  within  a 
few  degrees.  That  distinction,  however, 
has  been  made  in  the  twist  drills  (Fig.  179) 
of  constant  angle,  formerly  termed  “T.  & 

B.,”  and  being  of  10,  8,  and  6  pitch  respec¬ 
tively,  meaning  by  these  terms  one  turn  of 
the  spiral  in  a  length  of  10,  8,  or  6  diameters 
of  the  drill. 

Drills,  as  just  remarked,  are  thickened 
in  the  webs  towards  the  shank,  to  impart 
torsional  strength.  As  this  diminishes  the 
clearance  for  the  passage  of  the  chips  up  the 
grooves,  increase  twist  is  imparted  during 
manufacture  by  changing  the  speed  of 
rotation  of  the  drill  on  its  axis  as  it  is  fed  to 
the  cutter  which  forms  the  groove,  so  altering  the  pitch,  and  com¬ 
pensating  for  the  reduction  in  depth  of  cut.  In  the  constant-angle 
drills  made  by  the  Morse  Company  the  drill  is  rotated  at  a 
uniform  speed ;  but  the  angle  of  the  cutter  is  varied  to  widen  the 
groove  towards  the  shank. 

There  are  three  clearances  in  a  properly-made  twist  drill :  that 
from  the  point  to  shank,  or  longitudinal,  that  of  the  body,  or  trans¬ 
verse,  and  the  clearance  from  the  cutting  edge — the  backing-off. 
The  first  measures  from  about  .00025  to  -ooiS  per  inch  of  length, 
dependent  on  size  ;  the  second  about  half  a  degree 
(Fig.  180,  a,  a).  A  slight  width — “land” — is  left 
before  the  clearances  commence.  The  lip  clear¬ 
ance  is  from  12°  to  15°. 

The  angle  which  the  cutting  lips  of  twist  drills 
Fig.  180.  make  with  the  longitudinal  axis  of  the  shank  is 
59°  or  60°,  which  gives  straight  cutting  edges. 
The  grinding  lines,  when  such  are  used,  are  placed  slightly  to  one 
side  of  the  centre,  so  that  when  grinding  is  done  by  them  there  is 


134 


TOOLS. 


a  certain  angle  at  the  point,  which  is  the  most  efficient  for  clear¬ 
ance.  Thus  Fig.  i8i,  A,  shows  the  best  angle  of  the  point,  being 
about  135°  with  the  cutting  edge  ;  b  one  which  is  too  keen,  and  c 
one  with  no  angle,  showing  an  absence  of  clearance. 

The  clearance  of  both  lips  should  be  exactly  the  same ;  for,  if 
otherwise,  one  lip  will  tend  to  dig  in  more  deeply  than  the  other, 


t  I  I 

'A  B  C 

Fig.  181. 


with  the  result  that  the  torsional  strain  will  not  be  equally  balanced 
on  each  side  of  the  centre,  and  this  may  break  the  drill. 

If  drills  are  ground  by  hand  it  is  easy  to  test  the  amount  of 
clearance  given  by  means  of  a  rule  or  scale  (Fig.  182),  setting  the 
latter  on  each  side  in  turn,  and  revolving  the  drill  to  measure  the 
clearance  in  relation  to  the  height  of  the  cutting  edges.  A  square 
having  a  scale  marked  on  the  blade  will  answer  the  same  purpose. 


Two  systems  of  grinding  the  clearance  of  the  cutting  edges  of 
twist  drills  are  illustrated  by  the  diagrams  Figs.  183  to  186.  In  Fig. 
1 83  the  drill  is  being  revolved  about  a  constant  axis  a  while  grinding, 
which  gives  a  surface  corresponding  with  a  segment  of  a  cylinder. 
In  Fig.  184,  the  axis  of  movement  of  which  is  a,  b,  c,  the  revolu,- 
tion  gives  a  surface  corresponding  with  a  segment  of  a  cone.  The 


BORING  TOOLS  FOR  METAL. 


135 


effect  on  the  action  of  the  drill  is  that  of  cylindrical,  and  conical 
rollers,  respectively  shown  by  the  projections  in  Figs.  185  and  t86, 
running  in  conical  depressions.  In  Fig.  185,  the  clearance  angle 
a,  h,  r  of  A  is  different  from  that  at  d,  e,  foi  b,  so  that  if  the  clear- 


Fig.  185. 


Fig.  186. 


ance  is  right  at  the  centre,  it  is  excessive  at  the  outside.  In  Fig. 
186  the  clearances  at  by  c  and  d,  e,  f  axe  alike.  This  last, 
therefore,  should  give  increased  permanence  to  the  cutting  edge. 

The  Cleveland  Twist  Drill  Company  have  investigated  this 
subject  in  connection  with  a  special  apparatus,  which  recorded 
the  best  efficiencies  of  drills.  The  result 
is,  that  the  correct  form  is  found  to  be 
that  produced  by  grinding  to  the  segment 
of  a  cone  whose  axis  is  on  the  line  a,  b, 

Fig.  187,  and  at  an  angle  a,  b,  c  to  the 
axis  of  the  drill.  Now  it  is  evident  that 
a  cone  may  be  steep  or  flat,  and  according 
as  the  angle  which  a,  b  makes  with  the 
face  of  the  emery  wheel  is  varied,  will  the 
steepness  of  the  cone  be  lessened  or  in¬ 
creased.  Where  the  cone  is  steep,  and  the  point  of  the  drill  near 
the  apex,  the  curvature  at  the  point  of  the  drill  is  greater  than  under 
the  opposite  conditions.  The  result  is  that  considerably  more 
power  is  consumed  in  driving  the  drill,  as  much  as  20  per  cent. 


CV 


136 


TOOLS. 


in  one  experiment.  In  the  inverted  “cone”  formation  the  angle 
of  clearance  at  the  centre  is  greater  than  at  the  outside.  But  this 
must  not  be  excessive  in  amount,  or  the  edge  will  break  out  under 
heavy  feeding. 

If  the  drill  point  is  a  segment  of  the  surface  of  a  cylinder,  the 
clearance  angle  is  less  towards  the  centre  of  the  drill,  and  the 
corners  at  the  periphery  do  not  last  under  severe  duty. 

The  cutting  angle  of  the  drill  is  fixed  by  the  angle  of  the  spiral 
of  the  flutes.  As  in  other  tools,  practical  considerations  outweigh 
theoretical.  A  small  angle,  equivalent  to  a  fine  pitch  of  .spiral, 
is  best  for  cutting,  but  not  for  durability.  These  angles  range 
in  different  drills  from  18°  to  35°,  but  the  experiments  of  the 
Cleveland  Twist  Drill  Company  indicate  that  an  angle  of  27!° 
with  the  axis  is  the  best.  This  makes  the  spiral  groove  of  all 
drills  start  at  the  point  with  a  pitch  equal  to  six  diameters  of  the 


Fig.  188. 


Fig.  189. 


drill  blank.  The  difference  in  the  torsional  stress  on  a  drill  does 
not  vary  much  when  the  angle  of  spiral  with  the  axis  varies 
between  30°  and  25°. 

The  clearance  angle  of  the  drill  lip  is  fixed  at  the  outer  corners, 
where  it  should  range  between  12°  and  15°  with  a  plane  perpen¬ 
dicular  to  the  axis  of  the  drill  (Fig.  188). 

One  drawback  to  the  form  of  the  common  twist  drill  is  that  the 
actual  drill  point,  which  gives  an  oblique  connection  (Fig.  18 1, 
p.  134)  uniting  the  two  cutting  edges,  like  that  of  the  flat  drill,  never 
cuts.  It  has  simply  to  be  ground  into  the  metal  by  sheer  force  of 
feed.  The  only  course  open  is  to  reduce  that  edge  as  finely  as  pos¬ 
sible.  In  the  flat  drill  this  is  done  by  thinning  down  the  face.  In 
a  twist  drill  the  web  becomes  thicker  as  the  point  wears  back,  and 
the  evil,  therefore,  increases.  The  difficulty  is  minimised  in  drills 
of  large  and  medium  size  by  thinning  down  the  point,  as  in  Fig. 


BORING  TOOLS  FOR  METAL. 


137 


189,  a,  with  corresponding  increase  in  cutting  capacity,  without 
diminution  of  the  thickness  of  the  body  of  the  web. 

The  speeds  of  drills  are  settled  by  judgment,  and  experience. 
If  they  are  ground  properly,  and  fracture  at  the  edges,  the  speed 
may  be  increased,  but  the  feed  reduced.  If  the  extreme  edges 
alone  suffer,  that  may  be  taken  as  proof  that  the  speed  is  too 
high.  The  Cleveland  Company  recommend  tentative  speeds  as 
follows : — 30  ft.  per  minute  for  soft  tool,  and  machinery  steel,  35 
for  cast  iron,  60  for  brass,  and  a  feed  of  .004  to  .007  of  an  inch 
per  revolution. 

A  remarkable  fact  is  the  great  speeding-up  which  has  been 
successfully  accomplished  in  recent  years.  And  this  is  not  a 
question  of  tool  angles.  Even  when  these  angles  have  remained 
unchanged,  .speeds  have  been  increased  100  per  cent.  The 
explanation  is  to  be  found  in  the  fact  that  drills  are  made  better 
than  they  were,  and  that  experience  has  shown  how  they  are  to 
be  used  to  the  best  advantage.  But  no  hard-and-fast  rules  are 
possible. 

The  speed  of  a  drill  is  partly  governed  by  the  class  of  work 
being  done,  and  by  its  surroundings,  quite  distinct  from  the 
nature  of  the  material,  because  the  generation  and  removal  of 
heat  are  much  influenced  by  these.  A  parallel  case  is  that  of 
a  tool  point  gripped  in  a  tool-holder,  compared  with  a  solid  tool. 
The  first  is  not  capable  of  taking  such  heavy  cutting  as  the 
second,  because  the  heat  is  not  carried  away  so  readily.  So  in 
drilling,  heavier  cutting  can  be  done  with  drills  operating  in  large 
masses  of  metal  than  in  small  pieces.  In  the  latter  case,  the 
best  that  can  be  done  is  to  bring  the  small  piece  into  close  contact 
with  a  larger  mass  of  metal,  which  will  carry  off  the  heat,  either 
directly  on  the  table,  or  in  a  vice,  or  resting  on  a  large  support. 
The  worst  condition  is  to  have  a  non-conductor,  such  as  wood, 
underneath  the  work  being  drilled. 

Numerous  are  the  apparently  trivial  conditions  that  affect 
drilling  speeds.  To  drill  a  deep  hole,  from  which  the  chips 
escape  with  difficulty,  results  in  extra  friction,  and  diminution 
of  speed.  To  drill  shallow  holes,  in  which  there  is  no  trouble 
with  chips,  and  in  which  the  drill  has  many  brief  spells  of  rest 
when  changing  from  hole  to  hole,  is  favourable  to  increase  in 
speed.  The  nature  of  the  lubricant  used,  quite  apart  from  the 
quantity  employed,  is  another  factor.  The  frequency  or  other- 


TOOLS. 


138 

wise  with  which  the  edge  of  the  drill  is  restored  by  regrinding,  is 
another  important  element  in  speeding.  So  in  a  large  degree  is 
the  quality  of  the  steel  in  a  drill — the  degree  of  accuracy  wuth 
which  it  has  been  manufactured,  relieved,  and  ground  ;  and  almost 
as  important  as  any  condition  is  the  amount  of  care  and  skill 
brought  to  bear  upon  the  hardening  and  straightening.  These 
reasons  are  quite  sufficient  to  explain  why  differences  in  drilling 
speeds  amounting  to  fully  a  hundred  or  more  per  cent,  are  found 
in  practice. 

The  Speed  of  Drills  in  Revolutions  per  Minute. 


(Compiled  by  the  Cleveland  Twist  Drill  Company.) 


Diameter 

Speed  on 

Speed  on 

Speed  on 

of  Drill. 

Steel. 

Iron. 

.  Brass. 

1 

T« 

1150 

1750 

2000 

1 

575 

1000 

1200 

425 

700 

900 

i 

285 

450 

800 

t 

210 

325 

500 

1 

145 

220 

375 

1? 

125 

180 

315 

3 

4 

105 

130 

250 

i 

80 

105 

175 

I 

60 

90 

145 

55 

80 

130 

55 

70 

115 

li 

50 

60 

105 

45 

55 

100 

40 

50 

90 

f  3 

40 

48 

80 

li 

35 

45 

65 

2 

30 

45 

55 

2^ 

28 

40 

50 

2i 

28 

38 

45 

2i 

26 

35 

40 

2k 

23 

32 

40 

2f 

23 

32 

35 

2i 

20 

30 

35 

3 

20 

30 

35 

As  illustrative  of  the  fact  that  the  work  which  a  tool  is  capable 
of  doing  is  very  much  a  question  of  material,  the  case  of  the 
manufacture  of  the  twist  drills  themselves  may  be  noted.  When 
the  steel  rod  used  for  the  drills  has  been  selected  as  nearly  as 
practicable  of  the  same  quality,  and  been  annealed  as  nearly  as 


BORING  TOOLS  FOR  METAL. 


139 


possible  alike,  it  has  been  found  that  a  tool  which  will  turn  as 
many  as  twenty-five  blanks  i  in.  in  diameter  and  ii  in.  long, 
taken  from  one  lot,  without  regrinding,  when  turning  a 
lot  of  blanks  from  another  annealing,  the  tool  might  have 
to  be  re-ground  for  each  blank.  This  was  not  either  a 
question  of  hard  veins  or  non-homogeneity  of  any  kind 
in  the  steel,  but  simply  one  of  degrees  of  hardness  of  the 
annealed  material. 

These  facts  explain  why  drilling  speeds  vary  so  much, 
and  for  these  reasons  tables  given  are  only  valuable 
as  approximate  indications  of  what  should  be  expected 
of  drills  working  under  average  conditions. 

The  Morse  tables  are  those  which  are  generally 
accepted  as  giving  the  best  results.  They  are  not  the 
highest  nor  the  lowest.  A  table  of  especial  value,  com¬ 
piled  by  the  Cleveland  Twist  Drill  Company  from 
memoranda  furnished  them  from  about  five  hundred  of 
the  best  American  firms,  is  lower.  On  the 
contrary,  the  practice  of  the  Brown  &  Sharpe 
Company  is  much  higher  than  the  Morse  tables.  An 
abstract  of  the  Cleveland  table  is  given  On  the  opposite 
page.  Feeds  are  from  95  to  125  revs,  per  inch.  The 
Morse  feeds  are  ^  in.  drill,  feed  per  revolution  .005  in.  ; 
for  ^  in.,  .007  in. ;  for  f  in.  .010  in. 

A  good  deal  .of  drilling  is  now  being  done  with  tools 
of  high  speed  steels,  with  efficiencies  from  three  to  five 
times  greater  than  this  table  gives. 

The  ordinary  drill  is  a  tool  which  is  difficult  of  lubri¬ 
cation  in  deep  holes ;  and  this  is  rendered  more  so  by 
the  accumulation  of  chips,  which  clog  and  hinder  the 
action.  A  well-formed  twist  drill  drives  the  cuttings  out ; 
but  with  flat  drills,  the  occasional  removal  of  the  drill, 
and  the  clearance  of  the  chips  with  a  wire  is  often 
necessary  in  deep  holes. 

There  are  three  types  of  drills  in  which  the  difficulty 
of  lubrication  is  got  over  in  three  different  ways.  In 
one,  oil  tubes  are  let  into  grooves  in  the  drill  body 
between  the  grooves  (Fig.  190).  In  another,  oil  grooves 
are  drilled  in  the  drill  body  (Fig.  191).  In  the  third,  used  only 
in  turret  lathes,  a  single  large  oil  groove  runs  down  the  drill. 


Fig.  191. 


140 


TOOLS. 


Modern  arrangements,  too,  for  pumping  oil  under  pressure  are 
used  in  the  drills  in  question.  The  oil  pressure  fulfils  the  double 
function  of  keeping  the  drill  cool  and  of  forcing  out  the  chips. 
The  pressure  at  which  oil  is  fed  varies  in  practice  from  40  lb.  or 

50  lb.,  to  200  lb.  or  300 
lb.  on  the  square  inch. 

These  drills  are  costly 
as  yet,  but  they  are  an 
indication  of  probable 
future  developments.  As 
regards  relative  merits, 
holes  in  the  solid  seem 
preferable  to  tubes,  which 
may  w'ork  loose. 

In  making  the  twist 
drills  with  oil  holes  in  the 
solid,  the  blanks  are  first 
rough-turned,  and  then  at 
that  stage  the  oil  holes  are 
drilled.  The  drilling  is 
done  with  a  fixed  drill, 
the  blank  revolving.  Sub¬ 
sequently,  the  blanks  go 
to  the  smithy,  where  they 
are  heated,  and  twisted, 
until  the  oil  holes  take  the  same  twist  as  the  grooves  to  be  after¬ 
wards  cut.  Then  the  turning  is  finished,  followed  by  the  grooving. 

Fig.  192  shows  how  lubricating  drills  are  used  on  a  machine. 
A  flexible  tube  a  conveys  oil  from  the  pump  to  an  oil  box  b,  in 
which  the  collet  which 
holds  the  drill  revolves. 

The  oil-box  is  held  by  the 
extension  arm  c,  to  prevent 
it  from  partaking  of  the 
revolutions.  In  turret 
lathes  for  fixed  drills, 
other  simpler  arrangements  are  adopted. 

Fig.  193  shows  a  lubricating  drill  used  for  long  holes.  It  is 
screwed  to  a  metal  tube  of  the  required  length,  through  which  the 
lubricant  passes,  and  the  cuttings  escape. 


BORING  TOOLS  FOR  METAL. 


141 

The  best  results  in  drilling  are  obtained  in  gun-barrel  work. 
In  these  the  speeds  are  much  in  excess  of  those  in  the  ordinary 
machine  shop.  The  feeds,  however,  are  exceedingly  fine,  and 
these  results  would  not  be  possible  if  the  drill  itself  were  revolved. 
The  drill  is  stationary  and  the  work  revolves,  and  the  chips  are 
driven  out  by  a  flood  of  oil. 

The  drill  in  Fig.  194  has  the  oil  hole.  The  point  of  the  drill 
in  Fig.  195  is  stepped,  to  break  up  the  chips,  and  so  facilitate 


Fig.  194. 

their  removal  by  the  oil,  which  was  run  through  at  the  rate  of  two 
gallons  in  a  minute. 

It  is  a  rather  striking  fact  that  in  the  latest  twist-drill  making, 
hand-filing  in  the  lathe  is  resorted  to  in  order  to  produce  exact 
gauged  results.  The  reason  is  that  the  steel  used  is  of  a  hard, 
high-carbon  class,  and  even  though  the  tool  is  set  the  same,  the 
drill  blanks  do  not  all  come  out  the  same  size.  The  limit  is  a 
quarter  of  a  thousand  under  size,  and  nothing  over,  and  this  is 
the  fine  dimension  obtained 
by  hand  filing,  and  hand 
gauging.  This  includes  the 
filing  taper  for  clearance 
lengthwise. 

Twist  drills  are  ground 
on  the  point  only,  after 
hardening.  Though  the 
hardening  bends  and  warps  them,  this  is  corrected  by  hand 
work.  The  drills  are  heated  in  a  gas-flame  just  sufficiently  to 
permit  of  bending  without  drawing  the  temper,  and  squeezed 
under  a  press.  They  are  tried  on  a  perfectly  level  surface,  the 
light  underneath  the  drill  showing  whether  it  is  true  or  not.  A 
test  deflection  is  used  to  try  the  degree  of  hardness  of  each.  If 
the  drills  are  too  hard  they  break ;  if  too  soft,  they  bend. 

The  taper-shank  drills  predominate  over  the  straight-shank 
drills.  The  latter  can  only  be  used  in  small  sizes,  or  under  about 
f  in.  size,  because  drills  of  larger  diameter  cannot  be  driven  by  a 


142 


TOOLS. 


chuck  for  their  heaviest  duty.  The  taper  shank,  with  a  flat  at  the 
end  for  holding,  renders  the  drill  rigid  under  any  cutting.  Fig. 


196  shows  at  a  glance  the  proportionate  sizes  of  the  Morse 
standard  taper  drill  shanks. 


Fig.  197  shows  a  hollow  drill,  with  no  front  rake,  made 
specially  for  drilling  the  tube  plates  of  locomotive  boilers.  It  is 
hollow,  and  removes  an  annulus  of  metal. 


BORING  TOOLS  BOR  METAL. 


143 


Fig.  198  shows  two  drills  not  used  for  boring  holes,  but  for  slot 
drilling,  hence  the  reason  of  the  forms  of  their  cutting  edges.  They 
revolve  simply,  while  the  work  is  traversed  beneath  them,  and 
down  feed  is  not  imparted,  except  during  the  interval  between  the 
traverses,  a  performs  precisely  the  same  operation  as  b,  but 
illustrates  the  utilisation  of  worn-out  stumpy  twist-drills  by  suitable 


regrinding  of  the  cutting  edges.  These  can  be  used  with  advan¬ 
tage,  for  they  cut  faster  and  more  sweetly  than  the  usual  form  b. 
The  end  is  ground  flat,  and  then  a  clearance  angle  c  is  imparted 
behind  the  cutting  edge  b.  The  lowermost  figure  shows  the  end 
of  the  drill  turned  partly  round,  to  show  the  clearance  angle  c. 
The  small  concavity  ground  at  the  centre  of  a  and  b  separates  the 
two  cutting  edges,  and  the  revolution  of  the  drill  obliterates  the 
ridge  left  by  the  concavity  directly  it  is  formed.  Other  forms  are 


sometimes  given  to  slot  drills ;  but  these  are  suitable  for  cutting 
keyways  and  cottar-ways. 

Fig.  199  illustrates  a  very  special  form  of  drill  used  in  turret 
lathes.  The  tool  is  of  the  notched,  or  staggered  type  (see  page 
73),  the  object  of  which  is  to  increase  its  efficiency,  by  breaking 
up  the  chips.  Fig.  200  follows  and  smooths  the  holes  to  the 
exact  taper  required,  operating  thus  like  a  reamer,  a  class  of  tool 
to  which  we  now  give  attention. 

No  drills  work  so  accurately  as  to  be  depended  on  to  produce 
holes  to  perfect  gauge  fit.  If  a  hole  has  to  be  drilled,  so  that  a 
turned,  or  ground  pin  shall  fit  it  with  absolute  atcuracy,  it  is 


144 


TOOLS. 


necessary  to  finish  the  hole  with  a  solid  tool  of  the  exact  diameter 
of  the  hole  required.  This  is  much  more  necessary  when  there* 

are  several  holes  in  line.  The 
true  drills  cut  holes  in  solid 
metal,  which  distinguishes 
them  from  the  reamers,  rymers, 
or  broaches,  and  boring  tools, 
which  open  out  holes  already 
drilled.  Their  use  is  this  : — 
Since  it  is  practically  impos¬ 
sible  to  drill  holes  in  pieces 
of  work  through  which,  when 
assembled  together,  turned 
bolts  or  pins  have  to  pass  and 
fit  closely ;  the  holes  are  there¬ 
fore  drilled  in.  or  ^15-  in. 
less  in  diameter,  and  after  the 
work  is  assembled,  they  are 
finished  to  full  size  with 
reamers. 

Fig.  201,  is  one  form, 
the  principal  recommendation  of  which  is  that  it  is  easily  made 
in  the  shop.  It  is  a  solid  turned  bar,  flattened  at  the  end,  and 
ground  like  a  common  drill.  The  fine  cuttings  and  the  lubricant 
pass  up  the  grooves  a.  b  is  a 
much  superior  form,  the  nose  of 
which  is  serrated  into  a  number  of 
fine  cutting  points,  which  remove  the 
metal  in  very  minute  chips,  the  latter 
passing  up  the  grooves  cut  in  the 
solid  shank.  The  teeth  of  the  rose 
reamer  are  either  cut  on  a  convex 
edge  or  a  flattened  one.  In  neither 
case  do  they  remove  much  material.  P'ig.  202. 

c  is  better  adapted  for  rapid  cutting. 

The  grooves  are  milled,  and  pass  large  quantities  of  chips  readily. 
The  tools  shown  are  solid  reamers.  Hollow  tools.  Fig.  202,  with 
teeth  similar  to  c,  are  made  to  fit  on  arbors  of  standard  size,  a 
single  arbor  thus  taking  reamers  of  various  diameters.  There  are 
also  reamers  made,  the  cutting  edges  of  which  are  movable, 


BORING  TOOLS  FOR  METAL.  145 

and  so  adjustable  to  different  diameters,  some  examples  of  which 
follow : — 

The  Rogers  reamer  is  of  simple  construction,  involving  no 
screws  or  nuts.  The  blades,  Fig.  203,  are  fitted  into  dovetailed 


grooves,  which  are  inclined,  so  that  the  act  of  driving  the  blades 
up  the  grooves  expands  the  cutting  diameter.  After  driving  has 
been  done  to  the  limit  of  the  length  available,  fresh  blades  are 
inserted. 

The  Morse  reamer.  Fig.  204,  is  adjusted  by  means  of  a  tapered 


1 - - 

y - - 

r  ^ 

o' - z ' 

1 

8 

•  '  Fig.  204. 


plug  A,  which  is  screwed  into  the  body  of  the  reamer,  as  shown, 
and  acts  against  the  undersides  of  the  cutters  b,  of  which  there  are 
several.  The  nut  c  serves  to  tighten  the  whole  fitting  when  the 
desired  adjustment  is  obtained,  and  unless  this  nut  is  previously 
loosened  the  blades  and  plug  cannot  be  moved. 


Another  form  of  the  Morse  reamer  is  shown  in  Fig.  205,  where 
instead  of  the  thread  being  cut  on  the  small  end  of  the  tapered 
plug,  it  is  located  at  the  big  end,  as  seen.  A  special  spanner  em¬ 
braces  this  end,  and  engages  in  the  slots  cut  therein.  Otherwise 
the  principle  is  exactly  the  same  as  Fig,  204,  a  locking  nut  being 
provided  similarly. 


K 


146 


TOOLS. 


Another  reamer  which  has  blades  running  in  inclined  grooves 
is  shown  in  Fig.  206.  The  adjustment  is  effected  by  screwing  up 
the  tapered  nut,  and  securing  it  with  the  lock  nut,  so  that  the 
blades  are  firmly  held. 

Another  expanding  reamer,  Fig.  207,  has  blades  a  which  rest 
upon  a  circular  nut  b,  having  grooves  cut  in  it  to  take  the  blades, 
the  latter  being  inclined  as  shown.  The  ends  of  the  blades  are 

held  by  hooking  them  over  a 
sleeve.  Moving  the  latter  along 
the  body  causes  the  blades  to 
slide  up  the  grooves  in  the  nut 
B,  and  so  cut  larger,  the  nut  c 
being  the  means  of  sliding  d. 
To  lock  the  blades  firmly  when 
adjusted,  a  cap  e  is  screwed 
against  them,  and  locked  with  a  nut  behind,  f. 

The  fluted  reamers  cut  down  their  sides.  The  number  of 
flutes  varies  mainly  with  diameter,  but  different  ideas  prevail  with 
regard  to  the  number  of  teeth  which  a  reamer  should  have, 
whether  even  or  odd,  and  also  with  regard  to  the  shapes  of 
the  grooves. 

The  objection  to  the  reamers  with  an  equal  number  of  flutes 
is  that  each  tooth  is  balanced  by  only  one  set  opposite  to  it,  and 


c 

Fig.  207. 


therefore  if  a  hole  is  out  of  truth,  one  tooth  only  will  cut  in  that 
direction ;  but  if  the  spacing  is  unequal,  each  tooth  will  be 
balanced  by  two  on  the  opposite  side,  which  gives  a  better  chance 
of  true  work.  Sometimes  an  even  number  of  teeth  is  spaced 
unequally  to  produce  the  desired  result. 

The  objection  to  equal  spacing  lessens,  the  more  closely  the 
teeth  are  pitched,  because  as  the  latter  become  closer,  the  hole 
is  filled  up  better.  But  close  pitching  is  open  to  two  objections. 


BORING  TOOLS  FOR  METAL. 


147 


One  is  that  the  cuttings  do  not  get  away  so  freely,  the  other  that 
grinding  is  not  so  readily  done. 

In  grinding  reamers,  generally  the  axis  of  the  emery  wheel  is 
parallel  with  that  of  the  reamer.  Then  it  is  easy  to  see  that  close 
pitching  would  not  permit  the  wheel  to  clear  the  next  succeeding 
tooth.  The  use  of  small  wheels  is  objectionable,  because,  forming 
a  sensibly  concave  face,  they  weaken  the  cutting  edge.  It  is  a 
rule  that  the  largest  wheel  available  should  be  used,  in  order  to 
leave  a  face  practically  flat.  The  Pratt  &  Whitney  Company 
even  recommend  that  a  convexity  be  imparted  to  the  ground 
face.  Fig.  208,  a,  illustrates  the  eccentric  method  of  grinding, 
by  comparison  with  b,  the  usual;  a  therefore  resembles  the 
“formed,”  or  relieved  cutter  (see  page  118,  Fig.  155). 

Reamers  are  mostly  now  made  with  radial  teeth  in  milling 
cutter  fashion  in  preference  to  the  older  convex  grooves  of  the 
tap  style.  The  latter  act  more  by  scraping, 
and  the  amount  of  front  rake  changes  with 
grinding.  The  faces  of  the  teeth  are  gene¬ 
rally  radial.  Undercut  faces  tend  to  dig 
into  the  work,  especially  in  brass.  Sweetness 
of  cutting  is  further  secured  in  some  cases, 
as  in  milling  cutters,  by  setting  the  flutes 
spirally  instead  of  parallel,  between  which 
practice  is  divided.  Sometimes  the  spirals 
are  left-handed,  so  that  they  will  have  no 
tendency  to  draw  into  the  work. 

The  reamers  are  a  connecting  link  between  the  drills  and  the 
boring  tools.  The  use  of  a  boring  tool  presupposes  the  formation 
of  an  initiatory  hole  with  a  drill.  This  is  true  of  the  reamer  also. 
But  the  amount  of  metal  removed  by  the  latter  is  usually  slight, 
while  that  taken  out  by  boring  tools  is  often  large  in  quantity. 

big.  209  is  a  boring  tool  used  for  cutting  holes  in  sheet  metal 
when  the  holes  are  too  large  in  diameter  to  be  done  with  the 
common  drill.  It  is  formed  on  the  type  of  the  pin  drill.  A  hole 
is  first  drilled  in  the  plate  of  the  same  diameter  as  the  end  a  of 
the  bar,  the  bar  being  either  parallel  or  turned  down.  A  cutter 
B  is  wedged  into  a  slot  in  the  bar,  and  is  adjustable  for  radius. 
Owing  to  the  length  of  the  radius,  and  the  weakness  of  the  cutter, 
heavy  cuts  cannot  be  taken  without  chattering.  It  is  to  lessen 
risk  of  the  tool  point  digging  in,  and  chattering,  that  the  tool  is 


148  :  TOOLS. 

cranked  backward,  and  thickened  just  behind  the  cutting  point. 
These  tools  are  sometimes  made  solid — that  is,  the  cutter  and 
shank  are  forged  in  one.  Fig.  210  illustrates  another  type  of 
boring  tool  which  is  used  for  the  same  purpose  as  the  previous 


one,  only  that  it  is  better  suited  for  boring  deep  holes.  The 
range  of  the  cutter  b  in  Fig.  209  is  limited  in  depth ;  but  the 
cutter  in  Fig.  210  will  bore  a  deep  hole  as  well  as  a  shallow  one. 
To  lessen  the  stress  upon  the  cutter  the  work  is  divided,  and  the 
stress  nearly  balanced  between  the  edge  a  and  the  edge  b.  a 


Fig.  212. 


stands  a  little  below  b,  and  operates  first  on  a  area  of  metal  of 
radius  r ;  b  following,  operates  on  an  area  It  is  a  useful  tool 
for  cast  as  well  as  wrought  iron. 

In  these  tools,  though  a  hole  is  first  drilled  to  receive  the  end 
of  the  boring  bar,  the  work  done  is  not  an  enlargement  of  an 


BORING  TOOLS  FOR  METAL. 


149 


] 


\1- 

3 

existing  hole,  but  the  removal  of  an  annulus  of  metal  concentric 
with  the  drilled  hole.  With  the  true  boring  tools,  however,  the 
work  done  is  the  direct  enlargement  of  a  hole  already  cast  or 
drilled  nearly  to  size.  In  this  sense.  Fig.  2 1 1  may  be  considered 
related  both  to  the  reamer  and  the  boring  tool.  It  is  flattened 
like  a  drill,  and  cuts  like  a  boring  tool.  It  is  used  for  skimming 
round  the  edges  of  the  eyes  of  small  crane  hooks,  to  prevent  the 
rope  from  being  chafed.  One-half  the  hole 

is  first  smoothed,  then  the  hook  is  turned  < - 

over  to  do  the  other  half.  I  /~  n 

Fig.  212  is  a  common  form  of  tool  used  i _ 

for  miscellaneous  boring.  It  has  one  cutting 
edge  only ;  many,  however,  have  two. 

Boring  tools  of  this  general  type  are  made 
either  like  Fig.  212,  used  without  the  guid¬ 
ance  of  a  bush,  the  stiffness  of  the  bar  being 
sufficient  to  keep  them  steady  during  cutting  •, 
or  they  are  steadied  with  a  bush  fitted  into  a  Fig.  213. 

hole  in  the  table  of  the  drilling  machine. 

Bushes  of  the  same  outer  diameter,  but  of  different  bores,  are 
fitted  into  the  table  to  suit  boring  bars  of  different  diameters. 

Fig.  213  shows  double-ended  cutters  in  boring  bars,  on  which 
the  changes  are  rung  in  many  ways.  In  boring  large  holes,  a 
head  of  cutters  is  used,  fixed,  or  traversing  on  a  boring  bar.  A 
good  deal  of  information  relating  to  these  and  other  forms  of 
boring  tools  is  given  in  the  author's  “Engineer’s  Turning.” 

A  considerable  amount  of  boring  of 
a  rough  kind  is  done  with  a  flat  bit,  but 
it  is  not  adapted  for  precise  work  because 
^  it  lacks  rigidity,  and  wobbles,  following 
the  lead  of  a  roughly  cored  hole.  The 
Fig.  214.  bit  is  rendered  more  accurate  by  blocking 

it  with  wood,  of  nearly  semicircular  sec¬ 
tion  on  each  side,  so  filling  up  the  hole.  These  tools  cut  by  their 
leading  corners  chiefly. 

The  D  bits.  Fig.  214,  operate  truly,  whether  used  as  drills  or 
as  boring  tools.  The  radius  of  the  tool  equals  that  of  the  hole 
which  has  to  be  drilled  or  bored.  The  cutting  point  a  has  both 
top  and  front  rake,  and  the  edge  is  clear  of  the  work  at  b.  The 
lubricant  passes  along  the  groove  c,  usually  through  a  bit  of  copper 


TOOLS. 


150 

pipe.  Such  bits  will  drill  holes  up  to  about  3  in.  diameter.  In 
large  bits  the  actual  cutter  is  a  separate  piece  of  steel  screwed 
into  the  body.  The  latter  forms  three  parts  of  a  circle,  ensuring 
ample  guidance.  The  cutter  can  be  moved  forward  as  the  cutting 
end  becomes  worn  by  regrinding.  A  lip  is  formed  at  the  cutting 


Fig.  215. 


Fig.  216. 


edge  for  the  purpose  of  dividing  and  breaking  up  the  wide  shavings, 
and  so  facilitating  their  removal. 

Figs.  215  and  216  illustrate  arboring,  or  facing  tools  used  on 
the  drilling  machine.  They  resemble  pin  drills  in  fitting  into 
holes  already  drilled.  Fig.  215  is  a  solid  arbor;  in  many  the 
arboring  cutter  is  wedged  into  the  bar.  After  a  hole  is  drilled,  the 

boss  on  the  metal  round  the  hole  can  be 
faced  off  with  these  tools  at  the  same  set¬ 
ting,  with  the  certainty  that  the  face  will 
be  at  precise  right  angles  with  the  bore. 
These  are,  therefore,  used  very  extensively 
on  drilling  machines.  Fig.  216,  a,  shows 
one  that  acts  as  a  scrape,  b  one  that  has 
front  rake ;  in  c  the  side  teeth  are  absent, 
7  and  the  pin  is  inserted  with  a  taper. 

Fig.  217  is  a  bossing  tool.  The  ad¬ 
vantage  of  its  use  is  that  lever  bosses 
can  be  turned  without  resetting  the  work,  either  on  the  drilling 
machine,  or  in  the  lathe.  It  comprises  a  cutter  a  wedged  in  a 
bar  B,  the  bar  being  of  a  diameter  to  fit  the  hole  bored  in  the 
boss.  The  same  cutter  will  do  for  a  wide  range  of  bars.  The 
rate  of  downward  feed  is  proportional  to  the  diameter,  and  rate  of 
revolution  of  the  cutter. 


E 


B 


Fie;.  217. 


CHAPTER  XIII. 


Taps  and  Dies. 

Taps  and  Dies  a  compromise — Difference  between  these,  and  cutting  with 
Lead  Screw— Relation  between  a  Tap  and  its  Screwed  Hole — Initial  and 
Final  Diameters — Sets  of  Taps — Operation  of— Relieving— Cutting  Angles 
— Dies — Balance  of  Guidance  and  Cutting  Power — Size  of  Master  Taps, 
or  Hobs— Action  of  Dies — Notches — Guide  Screw  Stocks — Dies  used  in 
Screw  Machines — Echolls  Taps. 

IN  the  dies  and  taps  the  dithculty  has  ever  been  to  combine 
good  cutting  capacity  with  adequate  guidance,  and  with 
reasonable  permanence  of  edge.  One  condition  is  opposed 
to  the  other,  and  every  tap  and  die  is  a  compromise  between 
these  antagonistic  features.  We  will  consider  the  principles  on 
which  all  screwing  tackle  is  based. 

A  screw  is  a  wedge,  or  inclined  plane  wrapped  around  a 
cylinder,  and  is  therefore  formed  by  the  composition  of  two 
uniform  rectilinear  motions,  one  moving  around,  and  the  other 
along  the  cylinder.  By  varying  the  relative  rates  of  these  motions, 
screws  of  various  pitches  are  struck,  and  this  variation  is  the 
function  of  the  leading  screw,  and  change  wheels  of  the  screw¬ 
cutting  lathe,  and  of  the  chasing  lathe,  and  its  hobs.  In  each  of 
these  we  have  positive  guidance,  and  the  truth  of  a  screw  cut  by 
either  of  these  methods  depends  on  the  truth  of  the  guide  screw, 
or  the  hob  made  use  of.  These  methods  are  properly  reserved 
for  cutting  screws  of  considerable  length,  the  accuracy  of  which 
must  be  maintained  within  narrow  limits.  Some  lathe  guide 
screws  are  true  within  one-hundredth  of  an  inch  on  lengths  of 
from  4  to  6  ft.  Such  accuracy  would  not  be  possible  in  screws 
cut  otherwise  than  by  the  aid  of  an  accurate  master,  or  guide 
screw.  But  here  the  function  of  guidance  is  separated  from  that 
of  cutting,  and  there  is  no  analogy  between  a  thread  cut  with  a 
pointed  tool  controlled  by  a  lead  screw,  and  a  thread  cut  by 


'52 


TOOLS. 


means  of  taps  or  dies  drawn  into  or  over  the  work  by  their  own 
lead,  or  by  the  control  of  a  wrench  or  a  stock  held  in  a  workman’s 
hands.  For  while  the  functions  of  guidance,  and  control  are 
separate  and  distinct  in  the  first,  in  the  second  they  are  combined 
in  one  tool — a  distinction  which  is  very  important,  since  in  the 
first  a  narrow  edge  only  is  cutting,  and  in  the  second  the  cutting 
edges  encircle,  or  are  encircled  by  the  work. 

Observing  first  the  action  of  a  tap,  we  notice  that  good  results 
have  to  be  obtained  by  the  use  of  theoretically  bad  tools  in 
consequence  of  the  interfering  influence  of  the  depth  of  thread. 


Thus  in  Fig.  218,  in  which  the  relation  between  the  tap  and  its 
screwed  hole  is  shown,  this  difference  is  apparent.  The  diameter 
A  has  to  coincide  with  a'  at  the  termination  of  the  cutting  of  the 
thread,  and  b  with  b'.  But  at  the  commencement  of  the  cut, 
the  drilled  hole  into  which  a  has  to  work  its  passage  is  of  the 
diameter  b'.  Similarly  in  Fig.  219,  though  a  coincides  with  a' 
when  the  thread  is  finished,  yet  the  bottom  diameter  b  of  the 
thread  in  the  dies  has  to  embrace  a'  —the  diameter  of  the  thread 
at  its  point — before  it  can  cut  its  way  down  to  b'.  Hence  there 
is  want  of  coincidence  in  the  diameter  of  the  screwing  tools,  and 
of  the  work  done  by  them ;  and  further,  there  is  a  change  in 


TAPS  AND  DIES. 


153 


angle  from  root  to  point,  because  the  angle  of  a  screw  thread 
changes  with  its  diameter,  the  pitch  remaining  the  same.  (See 
Fig.  220,  where  the  difference  in  angle  is  shown  by  the 
slant  lines  a,  b,  projected,  that  to  a  representing  the 
point,  and  that  to  b  the  bottom  of  the  thread.) 

The  design  of  all  common  screwing  tackle  is  com¬ 
plicated  by  these  differences  in  initial  and  final  diameters, 
and  in  varying  angles,  and  for  this  reason  no  screwing 
tackle,  as  ordinarily  used,  is  more  than  approximately 
correct.  Such  tackle  is  in  greater  or  less  degree  a  prac 
tical  compromise,  a  striking  of  averages,  rendered  neces¬ 
sary  by  the  fact  that  taps  and  dies,  the  diameters  and 
angles  of  which  do  not  change,  have  to  cut  threads,  the 
diameter  and  angles  of  which  change  constantly  from  the 
first  starting  of  the  thread  to  its  completion.  This  is 
brought  home  most  forcibly  in  cutting  square  threaded 
screws ;  but  the  same  thing  exists  in  vee  threads,  though 
not  in  so  pronounced  a  manner.  In  screws  of  fine  pitch, 
the  difference  between  the  angles  of  root  and  point  is  so  Li 
slight  that  it  has  little  practical  effect  upon  results,  but  as 
screws  increase  in  pitch,  the  difference  has  to  be  reckoned  Fig-  220. 
with,  and  provided  for. 

Taps  are  designed  to  cut  internal  threads  gradually,  and  by 
this  means  the  difficulty  as  regards  difference  in  diameter  is 

rendered  practically  nil.  Three  taps, 
which  constitute  a  set,  are  called  re¬ 
spectively  a  “taper,”  or  “entering”; 
“  middle,”  or  “second” ;  and  “  bottom¬ 
ing,”  or  “  plug.”  The  taper  tap  (Fig. 
221,  a)  has  only  four  or  five  full  threads 
left  at  the  top ;  they  are  entirely  cut 
away  at  the  bottom,  leaving  the  dia¬ 
meter  there  the  same  as  the  bottom  of 
the  thread.  From  thence  the  depth 
of  thread  increases  uniformly  until  the 
full  depth  is  reached,  at  four  or  five 
turns  from  the  top.  'I'he  middle  tap  b 
has  all  its  threads  full  except  the  last 
four  or  five,  which  are  partially  tapered,  and  the  plug  tap  c  has 
all  its  threads  full.  When  a  deep  blank  hole  has  to  be  tapped. 


r 


Fig.  221. 


154 


TOOLS. 


the  first  tap  is  entered,  and  allowed  to  cut  as  far  as  possible ;  the 
second  follows  and  cuts  as  far  as  it  can  go ;  and  the  third 
finishes,  cutting  right  down  to  the  bottom.  If  a  thoroughfare 
hole  has  to  be  tapped,  the  first  or  second  tap  alone  will  suffice, 
going  right  through.  By  the  use  of  the  three 
taps  the  transition  from  the  small  to  the  large 
diameters,  with  the  corresponding  alterations  in 
angle,  are  effected  with  a  minimum  of  friction 
and  squeezing  of  the  material. 

But  it  is  evident  that  if  the  cross-section  of 
the  tap  were  that  of  a  complete  circle,  there 
could  be  no  leading  edge  to  cut,  and  no  relief 
for  the  following  surface.  Hence,  in  Fig.  222  the  section  of  the 
tap  threads  is  not  concentric,  but  they  are  backed  off,  and  the 
leading  or  cutting  edges  are  thereby  rendered  better  able  to 
penetrate,  wedge-like,  into  the  body  of  the  material,  on  the 
application  of  much  less  force  than  would  be  required  in  the 
^absence  of  the  backing-off.  Also,  the  following  surface  clears 
itself  of  much  frictional  contact,  entering  into  a  clear  space  cut 
for  it  by  the  leading  edge,  'fhis  backing-off,  or  relieving  is  very 
pronounced  in  the  entering  tap,  and  very  slight  in  the  middle 
and  finishing  taps,  because  the  bulk  of  the  material  is  removed 
in  the  first  operation,  while  the  last  two  smooth  down  inequalities 
left  by  the  first. 

The  tap,  therefore,  when  properly  formed  operates  as  a  true 
cutting  tool,  and  yet  it  is  much  less  favourably  shaped  for  cutting 
than  single-edged  tools,  to  which  it  bears  no  outward  resemblance. 
The  amount  of  backing-off  which  is  possible  is  extremely  slight. 
If  this  were  given  in  considerable  amount,  the  tap  would  lack 
guidance,  though  its  cutting  capacity  would  be  improved.  And 
while  a  common  turning  tool  has  a  top  rake  of  several  degrees, 
the  tap  rarely  has  any,  but  the  leading  or  cutting  edges  generally 
point  to  the  centre,  making  an  angle  of  90°  with  the  surface  of 
the  work.  Sometimes  the  faces  are  sloped  slightly,  to  give  a 
keener  angle,  but  it  is  usually  found  that  the  edges  are  weakened 
thereby,  and  do  not  endure  so  long  as  those  which  have  radial 
faces.  Taps  of  the  triangular  and  square  sections,  as  sometimes 
made  in  small  sizes,  cannot  be  ranked  with  true  cutting  tools, 
because  the  angles  are  too  great ;  but  being  small,  there  is  little 
friction,  and  so  they  perform  their  duties  fairly  well,  and  these 


TAPS  AND  DIES. 


155 


are  the  types  on  which  larger  taps  were  once  made.  Fig.  223 
shows  the  hob  or  master  tap  used  in  cutting  dies. 

Turning  to  the  dies,  we  note  also  the  due  balancing  of 
similar  qualifications — namely,  guidance,  and  cutting  power. 
Without  the  first,  drunken  and  wavy  threads  would 
result ;  in  the  absence  of  the  second,  the  material 
would  be  squeezed,  and  swaged  up  in  the  act  of 
removal.  Referring  to  Fig.  219,  the  want  of  coinci¬ 
dence  in  diameters  at  the  commencement  of  striking 
the  thread  is  apparent,  an  evil,  the  effects  of  which 
cannot  be  modified  in  the  case  of  solid  screw  plates, 
but  which  is  masked  by  the  smallness  and  shallow¬ 
ness  of  the  threads  in  screws  below  ^  in.  to  in.  in 
diameter.  The  difficulty  is  surmounted  in  screws  of 
larger  sizes  by  the  employment  of  adjustable  divided 
and  movable  dies,  set  in  a  screw  stock,  whereby 
minute  differences  in  diameter  are  effected  as  the 
threads  become  deepened.  There  is,  however,  the 
same  difficulty  as  regards  difference  of  angle  at  the 
commencement  and  termination  of  the  thread.  .'Mso 
there  is  the  difference  in  curvature.,  due  to  change  in 
diameter,  to  be  taken  account  of.  Let  us  see  how 
these  varying  elements  receive  embodiment  and  compensation  in 
the  dies  usuaUy  constructed. 

Every  one  knows  that  dies  are  cut  with  hobs  larger  in  diameter 


Fig.  223. 


'A 


Fig.  224. 


B 

Fig.  225.  Fig.  226. 


than  the  screws  which  are  to  be  cut  by  the  dies.  The  diameter 
of  the  hobs  (Fig.  223)  is  generally  larger  by  the  depth  of  one 
thread,  and  sometimes  by  two  threads,  than  that  of  the  screws 
to  be  cut.  Figs.  224  to  226  show  the  relative  situations  of  the 


TOOLS. 


T56 

dies  round  a  bar  at  the  commencement  and  termination  of  a  cut, 
A  showing  a  die  when  about  to  cut,  and  b  the  same  when  the 
thread  is  finished.  It  is  seen  at  once  that  the  cutting  power  of 
the  dies  is  due  to  difference  in  curvature,  for  if  it  were  possible  to 
use  dies  which  would  embrace  the  bar  closely  at  the  finish,  like 
Fig.  225,  they  could  not  cut  at  the  finish,  but  only  squeeze.  But 
in  Fig.  224  the  edges  cut  at  the  commencement,  a  penetrat¬ 
ing  before  the  body  of  the  die  thread  can  touch,  that  body  being 
thrown  off  the  bar  by  reason  of  the  curvature,  and  therefore 
furnishing  an  angle  of  relief  behind  the  points  a.  Presently  the 
curves  of  the  dies,  and  those  formed  therewith  coincide  for  a 
moment  or  two,  and  then  the  action  is  purely  squeezing,  until 
the  internal  corners  b,  b  effect  a  slight  penetration  into  the 
material,  and  so  acquire  a  cutting  capacity,  which  increases 
until  the  thread  is  down  to  its  proper  size,  the  curved  portions 
again  being  thrown  out  of  contact,  as  at  b.  Also,  since  the  dies 
are  symmetrical,  they  cut  equally  well,  whether  turned  right,  or 
left  handed. 

The  figure  shows  an  average  curvature,  and  notching.  But 
there  is  a  limit  to  each  of  these.  Sometimes  dies  are  cut  over 
a  hob  two  threads  deeper  than  the  screw  to  be  cut.  Some¬ 
times  the  notches  cut  away  a  larger  proportion  of  the  circle. 
Each  of  these  modifications  has  an  important  influence  on  the 
results.  If  dies  were  cut  over  a  hob  of  the  same  size  as  the  screw 
to  be  cut,  they  would  lose  guiding  power  entirely,  because  the 
merest  corners  would  touch  at  a,  a,  Fig.  225,  and  the  tendency 
would  be  to  start  drunken,  or  wavy  threads,  or  else  to  cut  con¬ 
centric  grooves ;  in  short,  they  lack  “  leading.”  When  they  are 
cut  over  hobs  of  two  threads  deeper,  they  have  abundance  of 
lead,  because  the  curvature  coincides  with  that  of  the  bar  at  the 
commencement,  but  they  squeeze  at  the  beginning,  while  at  the 
finish  the  corners  b  are  so  sharp  that  they  cut  with  great 
avidity,  increasing  as  the  thread  becomes  finished  (Fig.  226). 
Again,  if  too  much  of  the  circle  is  removed  by  the  notches,  leading 
power  is  diminished,  and  little  or  nothing  is  gained  for  cutting ; 
and  if,  on  the  other  hand,  there  are  no  notches  at  b,  the  dies 
could  never  cut  anything  smaller  than  the  hob  on  which  they 
themselves  were  formed,  because  once  the  curvatures  of  the  dies 
and  the  screw  threads  which  they  cut  coincided,  they  could  never 
get  below  that.  But  with  the  internal  edges  b,  b  coming  into 


T/IPS  AND  DIES. 


157 


play,  the  thread  diameter  can  be  reduced  below  the  diameter  that 
corresponds  with  the  dies  themselves. 

Clearly,  then,  in  whatever  manner  the  threads  are  cut  in  the 
dies  themselves,  their  action  is  necessarily  imperfect  at  some 
stage  of  their  operation,  and  this  is  borne  out  by  the  fact  that 
when  cutting  threads  by  them,  frequent  reversal  of  the  die  stocks 
is  necessary  to  ease  the  work — -a  practice  which  is  never  necessary 
with  the  chasing  tools  held  in  a  turret  lathe. 

The  guide  screw  stocks  used  to-day  are  the  survivals  of  early 
attempts  made  by  eminent  mechanicians,  to  overcome  the  evils 
of  the  enormous  amount  of  friction,  and  heat  which  the  common 
dies  generated,  and  their  squeezing  and  scraping  action,  which 
prevented  the  formation  of  threads  of  accurate  pitch,  kor  the 
earliest  of  these  we  must  go  back  to  1826,  when  a  Mr  Peter  Keir 
effected  an  improvement  which  was  the  forerunner  of  others. 
By  introducing  a  cutter  into  a  groove  sunk  in  a  die,  the  thread 
roughly  formed  was  deepened  by  a  true  cutting  action.  In  1828 
a  Mr  Jones  devised  an  improved  form  in  which  the  cutter  vyas 
clamped  upon  the  face  of  the  screw  stock.  In  France  several 
attempts  were  made  to  improve 
on  the  screw  plates  by  devising 
screw  stocks  with  movable 
guides,  and  movable  cutters. 

Mr  Bodmer  invented  a  guide 
screw  stock  with  vibrating  or 
oscillating  dies,  but  though  in¬ 
genious,  and  to  all  appearance 
perfectly  efficient,  it  never  came 
into  general  service.  This  was 
probably  due  to  its  rather  com¬ 
plicated  character.  The  well- 
known  guide  screw  stock,  and 
dies  of  Whitworth,  used  every¬ 
where  to-day,  was  the  first  really 
successful  attempt  to  strike  a 
suitable  mean  between  the  con 
trolling  and  cutting  actions.  In 

these  stocks  (Fig.  227),  there  is  one  die  which  acts  by  guidance 
only  to  the  other  two  which  do  the  cutting.  By  separating  the 
functions  of  the  fixed  guide  a,  and  movable  cutters  b  b,  practi- 


TOOLS. 


T58 

cally  perfect  threads  are  'se.cured,  while  variations  can  readily  be 
made  in  diameter  for  threads  of  different  sizes,  and  the  effects  of 
wear  are  not  apparent.  The  dies  are  cut  from  a  full-sized  master 
tap,  that  is,  one  twice  the  depth  of  the  thread  larger  in  diameter 
than  the  screw  to  be  cut,  and  they  are  therefore  of  the  same  curva¬ 
ture  at  the  start  as  the  blank  which  they  have  to  cut.  The  fixed 
die  cuts  at  the  start,  but  it  is  nearly  inoperative  afterwards,  except 
as  a  guide.  Only  one  movable  die  cuts  at  a  time,  the  other 
operating  when  the  motion  of  the  stock  is  reversed.  The  cutting 
faces  are  set  radially,  so  that  they  always  point  to  the  centre  of  the 
blank,  as  a  lathe  tool  does.  They  are  re-sharpened  by  grinding  on 
the  faces. 

In  an  earlier  die-stock  of  Whitworth’s  the  principle  of  letting 
the  cutting  predominate,  resulted  in  the  guidance  being  insufficient. 
But  that,  with  little  modification,  anticipated  the  dies  and  chasers 
of  to-day,  in  which  the  guidance  is  so  slight  that  they  cannot  be 
used  in  a  die-stock,  to  be  adjusted  over  its  work  by  hand,  unless 
a  guiding  bush  is  used,  though  they  give  the  highest  results  in  a 
screw  machine,  in  which  they  cannot  get  out  of  truth  diagonally 
in  relation  to  the  work  being  screwed. 

In  the  dies  used  in  screw  machines,  the  cutting  action  is  very 
keen,  so  that  in  all  screws  of  moderate  size,  one  traverse  is 
sufficient,  unless  fine  limits  are  desired.  The  results  are  obtained 
by  using  narrow  cutters,  by  which  the  guiding  action  is  diminished, 
so  that  instead  of  length  of  thread,  preponderating  over  notches, 
as  in  Figs.  224  to  226,  the  notched  portions  in  solid  dies,  and  the 
spaces  in  die  heads  are  much  greater  than  the  thread  surfaces. 
This,  with  the  better  leading  afforded  by  the  machines,  and  the 
improved  lubrication,  better  facilities  for  sharpening,  with  other 
matters,  have  rendered  tools  which  are  imperfect  theoretically, 
very  serviceable  in  practice. 

The  Echolls  patent  taps  (Fig.  228)  differ  from  the  ordinary 
ones  in  this That  every  alternate  tooth  is  omitted,  leaving  a 
space  which  permits  of  the  clearance  of  the  cuttings  without 
frequent  reversal  of  the  tap,  this  result  being  shown  in  Fig.  229. 
It  is  claimed  that  the  resistance  to  tapping  is  from  30  per  cent, 
to  50  per  cent,  less  with  these  than  with  the  common  ones.  Fig. 
228  shows  the  taper,  the  plug,  and  the  bottoming  taps. 

Expanding  taps,  and  taps  with  inserted  cutters  are  used  to  a 
moderate  extent,  but  not  much  in  ordinary  shop  practice. 


TAPS  AND  DIES. 


159 


Threads  can  be  cut  with  dies  of  -the  opposite  hand.  1  his  is 
a  mechanical  curiosity  of  no  practical  value.  It  depends  on  the 
size  of  hob  over  which  dies  are  cut.  It  could  not  be  done  with 
dies  cut  over  hobs  two  threads  larger  than  the  screw,  it  can  with 


Fig.  229. 


those  cut  over  hobs  of  the  same  size  as  the  screw,  and  in  which 
the  extreme  points  only  come  into  contact  with  the  screw  blank 
at  the  beginning  of  the  work.  At  this  time,  therefore,  the  dies 
will  yield  to  pressure  turning  them  with  a  left  or  a  right  hand 
lead,  and  once  started,  the  dies  will  follow  the  lead. 


SECTION  IV. 

PERCUSSIVE,  AND  MOULDING  TOOLS. 


CHAPTER  XIV. 

Punches,  Hammers,  and  Caulking  Tools. 


The  Punch — Spiral  ditto — Taper  of  Punch — Burr — Various  Punches — Drifts — 
Hammers — Varieties  of — Force  of  Blow — Mallets — Caulking  Tools— for 
Plates— for  Pipes. 


T 


'HE  punch  is  an  annular  shearing  and  detrusive  tool  having 
angles  of  90°,  or,  rather,  very  slightly  less,  by  from  to  i  ’ 
due  to  the  clearance  of  the  body.  The  power  required 
to  operate  a  punch  is  so  great  that  the  practical  limit  to  thickness 
of  the  plate  punched  is  the  diameter  of  the 
punch  itself.  Spiral  punches  have  been  designed 
to  produce  a  shearing  cut  ;  but  they  have 
found  comparatively  little  favour,  because  they 
are  less  easily  kept  in  order  than  the  ordinary 
types. 

Kennedy’s  spiral  punch  (Fig.  230)  has  been 
used  with  good  results.  Mr  Webb,  of  Crewe, 
who  first  gave  it  an  extended  trial,  found  that 
the  strength  of  the  same  steel  plates  after  using 
the  spiral,  and  the  common  punch,  equalled 
63,929  lbs.,  and  58,579  lbs.  respectively,  a  differ¬ 
ence  of  5,350  lbs.  in  favour  of  the  spiral  tool. 

The  circumference  of  a  punch  is  very  small  by  comparison 
with  the  length  of  shear  blades.  The  action  is  so  violent  that  the 
severed  edges  are  left  torn  and  ragged  and  fibrous,  and  metal  in 
the  immediate  vicinity  is  ruptured  with  minute  cracks.  If  a  clean 
shorn  surface  is  required,  this  can  be  produced  in  thin  work  only, 
because  the  shearing  force  required  for  thick  plates  is  so  great  that 


-Fig.  230. 


PUNCHES,  HAMMERS,  6-  CAULKING  TOOLS.  i6r 


no  chisel-like  tools  of  the  purely  cutting  type  would  endure  it. 
These  last  come  in  when  wire  is  to  be  severed,  in  which,  though 
the  apparent  action  is  that  of  shearing,  there  is  no  shearing  cut  at 
all;  nor  is  it  necessary,  because  the  area  severed  is  so  small. 
The  cutting  angle  of  these  is  much  the  same  as  those  of  the  tools 
for  turning  wrought  iron. 

Fig.  231  shows  the  common  form  of  punch,  and  its  bolster, 
tapered  to  allaw  the  burr  to  fall  through. 

A  rule  for  the  angle  of  the  punch,  and  clearance  between 
punch  and  die,  is  to  draw  an  acute  angled  triangle  with  a  2  in. 
base,  and  1 2  in.  high,  and  on  that  draw  a  line  across  where  the 
width  is  equal  to  the  diameter  of  the  punch,  and  another  between 


Fig.  231. 


I 


I 


Fig.  232. 


at  a  distance  equal  to  the  thickness  of  the  plate  to  be  punched, 
and  there  obtain  the  diameter  of  the  hole  in  the  die. 

Another  rule  for  the  taper  of  punches  and  their  dies,  which 
was  arrived  at  as  the  result  of  experiments,  is  as  follows  (Fig.  232): — 
Draw  a  triangle  having  a  base  i  in.  in  length,  and  two  equal  sides 
meeting  at  a  distance  of  5;^  in.  These  will  give  the  angle,  on 
which  at  the  height  corresponding  to  the  diameter  of  the  punch, 
set  off  the  latter,  and  below  it  the  thickness  of  the  plate  to  be 
punched.  Below  this,  the  size  of  hole  of  the  bolster,  the  diameter 
of  which,  therefore  varies  with  the  thickness  of  plate.  Its  taper 
must  be  at  least  as  much  as  that  given  by  the  triangle. 

The  common  punch  has  been  responsible  for  many  cracked 
plates,  hence  the  reason  why,  in  good  work,  no  riveting  is  per- 

L 


i62 


TOOLS. 


Fig.  233. 


mitted  to  be  done  as  the  plates  leave  the  punch,  but  reamering  is 
insisted  on.  From  twenty  to  twenty-five  years  ago  this  was  a 
burning  question  in  the  plating  and  boiler  shops,  since  which 

time,  practice  has  settled  down  either  to 
punching,  followed  by  reamering;  or  drilling, 
the  latter  being  generally  adopted  in  boiler 
work,  while  both  methods  are  adopted  in 
bridge  and  girder  work. 

The  punching,  or  burr  produced  by  a 
common  punch  is  never  so  thick  as  the 
plate  from  which  it  is  driven.  It  is  always  concave,  and  convex 
on  opposite  sides.  It  has,  however,  the  same  specific  gravity  as 
the  plate,  which  shows  that  the  material  which  represents 
the  difference  between  the  contents  of  the  hole  and  that 
of  the  punching  has  been  squeezed  into  the  plate.  A 
zone,  or  annulus  round  the  hole  is  thus  stressed,  and 
cracked,  and  suffers  in  consequence.  This  zone  only 
extends  about  one  half  of  a  millimetre,  so  that  in  reamer¬ 
ing  out  a  hole,  say,  from  gV  in.  to  in.  larger,  the 
stressed  metal  is  removed. 

The  form  of  punch  shown  in  Fig.  233  has  been  Fig.  234. 
proposed  in  order  to  obtain  a  true  shearing  cut, 
instead  of  a  detrusive  one,  but  it  has  not  found  much  favour. 

Multiple  punches  are  arranged  in  machines  in  numerous 
designs,  and  fill  a  large  place  in  the  economical  manu¬ 
facture  of  bridges  and  girder  work. 

Among  the  minor  punches  are  those  having  special 
functions,  as  the  following : — The  centre  punch  (Fig. 
234)  used  for  popping  centres  and  centre  lines  on 
engineers’  work.  The  brad  punch,  used  by  woodworkers 
for  driving  the  heads  of  nails  below  the  surface,  so  that 
they  may  be  covered  and  concealed  by  stopping.  The 
small  hand  punch  employed  by  packing-case  makers  for 
forming  the  nail  holes  in  the  hoop  iron  bonding.  The 
punches  of  the  repouss^  worker,  which  do  not  make  holes. 


"V" 


Fig.  235.  but  indent  the  surface  of  the  metal  sheet,  so  producing 
the  designs  required. 

Fig.  235  is  a  centre  punch  for  special  service,  its  function 
being  to  set  in  the  centres  of  rivet  holes  through  holes  in  a  plate 
already  punched  to  another,  the  holes  in  which  have  to  match  it. 


PUNCHES,  HAMMERS,  cS-  CAULKING  TOOLS.  163 

I3rifts  are  used  in  association  with  the  punches  for  enlarging 
holes,  and  for  pulling  holes  in  plates  into  alignment  with  each 
other.  The  first  named  are  allied  to  the  moulding 
tools.  Fig.  236  shows  the  drifts  used  for  pulling 
holes  into  line.  Fig.  237  is  a  drift  employed  for 
the  enlargement  and  smoothing  of  holes  already 
made  in  smith’s  work  by  punching.  Fig.  238  is 
one  of  a  more  special  character  used  under  a  power 
hammer,  by  which  flanged  rings  are  produced  from 
annular  discs.  In  both  these  last  it  is  necessary 
to  support  the  work  on  a  bolster  in  opposition  to  Fig.  236. 
the  drift. 

Few  tools  vary  more  greatly  in  form  than  the  hammers.  Every 
trade  has  its  own  special  forms,  and  some,  as  boiler  makers,  and 
tinsmiths,  include  a  large  number. 

With  the  exception  of  the  claw  hammers,  the  claw  of 
which  is  used  for  withdrawing  tacks  and  nails,  scaling 
hammers,  and  a  few  of  that  class,  both  ends  or  panes  of 
hammers  are  used  for  percussive  purposes,  d'he  panes 

237.  are  of  circular  forms,  large  or  small  in  diameter,  or  they 
are  oblong,  or  hemispherical  in  form.  When  oblong  they 
are  long  pane,  as  when  the  longer  portion  runs  in  the  same 
direction  as  the  handl-Q  j  cross  pane  when  they  run  across. 
They  are  ball  pane,  when  of  more  or  less  hemispherical  form. 
Variations  occur  besides  in  the  lengths  of 
hammer  heads,  some  being  short,  others 
long,  some  straight,  others  curved.  In 
every  case  the  design  is  suited  to  the 
functions  of  the  hammer.  Nothing  comes 
by  chance.  Thus  the  hammers  of  the  boiler¬ 
maker  and  the  patternmaker  are  both  long, 
so  that  they  may  get  down  into  angles, 
which  short  hammers  would  not  reach. 

The  shoemaker’s  hammer  is  broad,  for  work¬ 
ing  on  leather  soles.  Other  hammers,  such 
as  some  of  the  smith’s  sledges,  and  miners’ 
hammers  and  planishing  hammers,  have  both  faces  alike  broad. 
Others  combine  an  axe-like  edge,  with  a  hammer  pane,  as  in  some 
quarrying  tools. 

Fig.  239,  A,  shows  the  most  familiar  form  in  which  the 


164 


TOOLS. 


hammer  occurs.  It  is  just  a  carpenter’s  tool  for  general  service. 
B  is  a  better  form,  because  longer,  and  the  narrow  pane  is  more 


serviceable  for  reaching  into  the  deeper  parts  of  work  for  tapping 
or  driving  brads.  The  group  in  Fig.  240  comprises  engineer’s 

and  boilermaker’s  hammers,  a  being 
cross  pane,  b  long  pane,  c  ball 
pane,  d,  e,  f,  are  ordinary  boiler¬ 
makers’  hammers,  used  chiefly  in 
rivet  work,  G  is  a  hammer  in  name 
only,  being  strictly  a  percussive 
chisel  used  for  detaching  the  scale 
from  boilers.  Fig.  241  is  a  group 
of  sledges,  a  straight  pane,  b  cross 
pane,  c  the  common  double-faced 
sledge,  D  ball  pane,  e  is  a  round- 
faced  sledge  used  by  boilermakers 
for  flanging  tubes.  Fig.  242  is  a 
smith’s  monkey,  slung  with  a  rope 
by  the  eye  a,  and  swung  back  in 
an  arc  of  a  circle,  and  released 
by  a  rope  round  the  eye  b.  It 
is  used  for  upsetting  work  laid 
horizontally. 

Hammers  are  fitted  with  handles  of  medium  length  usually, 
but  the  sledges  are  exceptionally  long  to  permit  of  their  being 
swung.  Wedges  hold  the  handles  in  a  doubly  tapered  eye,  or  in 


Fig.  240. 


PUNCHES,  HAMMERS,  CAULKING  TOOLS.  165 


some  cases  the  hammer  head  is  prolonged  into  straps  which 
embrace  the  handle  through  which  they  are  riveted. 


Fig.  241. 


Fig.  242. 


Hammers  are  fitted  to  power-operated  machines,  both  of  the 
gravity  drop,  and  steam  types. 

Hammers  are  made  of  solid  steel, 
or  of  iron,  steel-faced.  They  are  sold 
by  weight,  which  in  different  kinds 
may  range  from  a  few  ounces  in  hand 
hammers,  to  14  lbs.  in  sledges.  The 
force  of  a  blow  delivered  is  governed 
by  the  mass  of  the  hammer,  and  the 
distance  through  which  it  is  swung. 

The  latter  is  under  the  control  of 
the  workman.  Its  amount  is  capable 
of  calculation,  and  is  given  in  text 
books,  but  in  practice  it  is  a  matter 
of  mechanical  instinct,  and  judgment. 

The  net  result  is  that  of  developing 
a  force  for  a  short  time  equal  to  that 
produced  by  the  continued  pressure 
of  a  steady  load  ;  and  is  the  same 
problem  as  that  of  the  steam,  or  drop  hammer,  compared  with 
that  of  the  hydraulic  press. 

The  mallets.  Fig.  243,  a,  are  a  special  form  of  hammers,  the 


i66 


TOOLS. 


reason  for  their  use  being  the  bruising  effect  of  steel-faced 
hammers  on  tool  handles  of  wood.  One  exception  to  this  is  a 
wooden  mallet  c,  used  on  a  stonemason’s  steel  chisel.  Mallets 
are  bonded  in  steel,  b,  in  some  cases.  Fig.  244  is  a  boilermaker’s 


mallet,  used  for  levelling  plates,  without  risk  of  bruising  them. 
The  handle  of  a  mallet  is  fitted  with  a  taper,  the  larger  end  of 
which  is  outward,  so  that  the  head  will  become  tighter,  instead 
of  flying  off  by  centrifugal  force. 


B 


Fig.  245- 

Midway  between  the  steel  hammers  and  the  wooden  mallets 
are  the  lead,  and  copper  hammers  of  the  fitter,  and  machinist, 
plain  cylindrical,  or  barrel-like  in  outline.  These  are  used  for  the 
same  objects  as  the  mallets  of  wood,  namely,  to  avoid  bruising 

metal  work  by  the  act  of  driving. 

Caulking  tools  belong  to  the  per¬ 
cussive  class,  because  they  are  actuated 
by  hammers.  Their  function  is  mainly 
that  of  burring  up  the  edges  of  steel 
and  iron  riveted  plates,  in  order  to 
render  them  tight  against  water,  or  gases,  hence  the  edges  of  the 
tools  are  roughened  up,  or  serrated  (Fig.  245).  The  difference  in 
A  and  B  IS  that  a  is  narrow,  and  does  not  operate  on  the  entire 
thickness  of  the  edge,  but  only  on  that  portion  adjacent  to  the 
adjoining  plate,  while  b  is  as  deep,  or  deeper  than  the  plate 


Fig.  246. 


PUNCHES,  HAMMERS,  Sr  CAULRING  TOOLS.  167 


thickness,  and  is  used  for  broad  finishing.  Both  are  varied 
also,  in  being  made  convex  on  the  lower  face  to  suit  curved 
plates.  These  are  hand  tools,  but  the  types  are  embodied  in 
pneumatic  caulking  tools,  which  deliver  several  hundreds  of 
blows  in  a  minute. 

Fig.  246  is  a  caulking  tool  of  another  kind,  used  for  driving 
the  yarn,  and  lead  used  in  caulking  the  socketed  and  spigoted 
joints  of  water,  and  gas  mains.  These  are  made  both  straight, 
and  curved  in  section,  as  shown  in  the  figure. 


CHAPTER  XV. 


Moulding,  and  Modelling  Tools. 

Two  Great  Groups — That  which  is  Related  to  Percussive  Tools — Smiths’ 
Flatters,  Fullers,  and  Swages — Their  Co-relation  to  the  Fibrous  Char¬ 
acters  of  the  Materials — Trowel  Group — Plasterers’  Tools — Moulders’  ditto 
— Cleaners — Sleekers  of  Various  Sections. 


There  are  large  numbers  of  tools  which  are  related  to  the 
percussive  group,  because  many  of  them  are  actuated  by 
hammer  blows.  This  group  includes  on  the  one  hand 
tools  which  operate  on  iron  and  steel  at  a  red  heat,  and  on  the 
other  those  which  produce,  or  finish  the  contours  of  moulding 


Fig.  247. 


sand,  modelling  clay,  masons’  mortar,  and  plasterers’  materials. 
They  are  employed  in  many  trades. 

Taking  first  the  group  which  moulds  the  forms  of  iron  and 


Fig.  248. 


Steel  while  white,  or  red  hot,  the  value  of  these  depends  on  the 
viscous  or  fibrous  character  of  these  materials.  None  of  these 
tools,  for  example,  would  be  of  any  service  on  cast  iron,  or  brass. 
The  representative  of  the  class  is  the  smith’s  flatter  (Fig.  247),  and 


MOULDING,  AND  MODELLING  TOOLS.  169 


its  allied  form,  the  set  hammer.  Curved  tools  developed  from 
these  are  the  hollow  swages  (Fig.  248),  and  the  fullering  tools 
(Fig.  249,  A  and  b),  each  of  which  occurs  in  several  dimensions, 
and  many  curvatures.  A  special  adaptation  is  the  rivet  sett  c,  the 
working  face  of  which  is  an  exact  counterpart  of  the  tail  of  the 
rivet  which  it  finishes.  Special  forms  of  fullering  tools  used  on 
steam  hammer  work — hence 
having  long  handles  —  are 
shown  in  Fig.  250.  A  is  of 
circular  section,  and  is  used 
for  fullering  down  bars  by  a 
succession  of  shallow  con¬ 
cavities.  B  is  used  to  fuller 
bevelled  faces  to  a  definite 
angle,  and  c  is  employed  for 
making  scarfed  ends  for  welding.  These  tools  are  laid  upon  the 
work  by  the  smith,  and  struck  by  the  tup  of  the  hammer. 

This  is  merely  a  typical  representation  of  a  group  which  is 
numerically  large.  Neither  of  them  cuts,  or  removes  any  material, 
but  simply  moulds  it  into  shapes  which  are  nearly  or  quite  the 
counterpart  in  form  of  the  acting  portion  of  the  tool. 

^(LID==^ 


Fig.  249. 


Fig.  250. 


So  little  suffices  to  sever  fibre,  and  the  weakening  effect  is  so 
great,  that  when  it  is  necessary  to  reduce  the  area  of  a  bar,  or  to 
bend  it,  or  to  groove  it,  sharp  tools  are  never  used  to  set  down  the 
metal.  The  effect  of  nicking  a  bar  with  a  sharp  tool  is  to  sever 
the  grain,  and  cause  a  crystalline  fracture.  This  is  seen  in  the 
method  adopted  in  smithies  in  cutting  off  bars.  The  latter  are  laid 
on  the  anvil  chisel,  and  nicked  all  round  with  the  sett,  and  struck 


170 


TOOLS. 


with  a  hammer,  so  forming  a  keen  recess  encircling  the  bar. 
When  broken  with  a  smart  blow,  the  surface  presents  a  crystalline 
appearance,  very  like  cast  iron.  Put  the  same  bar  into  a  testing 
machine,  and  pull  it  slowly  asunder;  the  area  at  the  fracture  will 
be  much  reduced,  the  fibre  will  be  drawn  out  like  a  bundle  of 
muscle,  and  no  crystallisation  at  all  will  be  apparent.  If  the  bar 
is  bent  round  by  hammering  until  it  fractures,  the  appearance  will 
be  very  similar.  The  fibres  will  be  strained,  and  severed  irregu¬ 
larly  on  the  outer  radius,  and  crumpled  up  and  corrugated  on  the 
inner  radius. 

Hence  all  the  tools  used  in  the  formative,  or  moulding 
processes  of  the  smithy  have  edges  more  or  less  rounding.  The 

fullers  —  straight,  hollow,  round 
faced ;  and  the  flatters,  &c.,  all 
have  edges  more  or  less  convex. 
They,  therefore  squeeze  and  mould 
the  outlines  of  the  work,  but  they 
do  not  cut  it.  If  we  could  see  the 
grain  of  a  bar  after  it  had  been 
set  down  with  any  of  these  tools,  it 
would  show  fibre  bent,  squeezed, 
elongated,  but  with  its  con¬ 
tinuity  unaffected ;  its  formation 
is  changed,  but  its  strength  is  left 
intact  after  the  employment  of 
such  tools. 

The  great  group  of  moulding 
tools  is  perhaps  best  represented  by  the  trowel.  Its  most  familiar 
type  is  that  used  by  slaters  and  masons.  Fig.  251,  a,  or  by 
plasterers,  b.  The  trowels  of  the  moulder  are  like  a  with 
variations  in  outline,  as  heart,  square,  dog-leg,  &c.  The  func¬ 
tions  of  all  alike  are  to  smooth  surfaces  of  plastic  substances, 
level  or  nearly  so.  The  numerous  trowel-like  tools  which 
are  derived  from  the  flat-faced  type  are  employed  in  the  work  of 
finishing  moulded  forms.  The  plasterer’s  tool  c  is  one  only  in  a 
group.  The  moulder’s  tools,  of  which  a  selection  are  shown  in 
Fig.  252,  are  employed  for  work  in  sand. 

The  moulder  uses  his  trowel  for  sleeking  the  joints  and  the 
flat  faces  of  moulds,  for  mending  up  sand  that  is  broken  down, 
for  laying  on  plumbago,  and  other  functions.  In  Fig.  252,  a  is 


Fig.  251. 


MOULDING,  AND  MODELLING  TOOLS.  17 1 


a  flange  cleaner,  used  for  mending  up  and  sleeking  deep  flanges 
before  and  after  blackening.  Vertical  faces  are  smoothed  with  the 
flat  blade,  and  the  bottom  with  the  return  end,  with  which  also 
loose  sand  is  picked  up.  The  sleekers  form  a  large  group.  One 
of  these  used  for  deep  moulds  is  shown  at  b.  It  has  flat  ends, 
and  convex  faces  adjacent,  c  is  a  beading  tool  for  flanges,  made 


Fig.  252. 


in  various  widths,  and  radii.  D  and  E  are  radius  tools  used  in 
pipe  work,  and  for  the  general  finishing  of  curves.  These  also 
are  made  in  various  radii,  f  is  a  type  of  tool,  curved  in  two 
directions,  termed  egg,  and  button  sleekers,  for  smoothing  hemi¬ 
spherical  forms.  Internal  and  external  angles  are  smoothed  with 
tools  like  G  and  h.  Both  faces  may  be  straight  longitudinally  as 
in  H,  or  one  straight,  and  one  curved  like  g. 


CHAPTER  XVI. 


Miscellaneous  Tools,  and  Tool  Handles. 

Spanners — Wrenches — Ratchet  Braces — Woodworkers’  Braces — Tap  Wrenches 
— Pincers — Pliers — Tongs — Tool  Handles — Forms  used  for  Thrusting — 
for  the  Mallet — for  Turning — for  Planes — for  Swinging — Summary. 

IN  this  chapter  we  discuss  as  briefly  as  possible  a  considerable 
number  of  tools  which  have  no  particular  relationship  to 
each  other,  or  to  the  great  groups  which  have  been  already 
considered. 

Spanners,  and  wrenches  are  terms  often  used  loosely  to  dis¬ 
tinguish  two  diflerent  tools.  In  strict¬ 
ness,  however,  a  spanner  is  an  instru¬ 
ment  with  solid,  or  fixed  jaws,  while  the 
wrench  with  movable  jaws,  is  hence  often 
termed  a  shifting  spanner.  Spanners 
are  single,  or  double  ended,  wrenches 
have  but  one  end  ;  the  variations  in  the 
designs  of  spanners  are  not  numerous,  those  of  wrenches 
are. 

The  spanners  are  straightforward,  or  have  their  jaws 
set  at  an  angle  with  the  shank.  The  object  of  the  latter 
is  to  permit  the  instrument  to  turn  a  nut  with  the  least 
amount  of  movement,  a  property  which  becomes  very 
valuable  when  working  in  confined  spaces.  The  most 
suitable  angle  for  this  is  15°  (Fig.  253).  The  explana¬ 
tion  is  this :  A  straight  spanner  will  turn  a  square  nut  in 
an  angle  of  90°,  or  a  hexagon  one  in  60°.  If  a  spanner 
has  an  angle  of  15°,  it  will  turn  a  hexagon  nut  in  a  space  pig.  254. 
of  30°.  The  sizes  of  spanners  are  given  in  the  diameters 
of  the  bolts  they  are  suitable  for.  Thus  a  i  in.  spanner  means 
one  for  turning  the  nut  of  an  inch  bolt,  and  the  jaws  would 


MISCELLANEOUS  TOOLS. 


173 


measure  if  in  the  opening.  The  length  of  shank  is  from  eight 
to  nine  times  this  width. 

A  box  spanner  (Fig.  254)  is  used  when  a  nut  lies  down  in  a 
circular  recess,  so  that  a  common  spanner  cannot  be  used.  The 
box  spanner  is  turned  by  a  lever  or  podger  inserted  in  the  hole  a. 


Fig-  255- 

The  wrench,  or  shifting  spanner  occurs  in  numerous  designs. 
The  best  are  those  with  double  bars  to  hold  the  fast  jaw  parallel. 
In  some  wrenehes  the  adjustment  is  effected  by  turning  a  milled 
nut,  in  others,  by  turning  the  handle.  In  one  form  the  nut  is  en¬ 
closed  within  the  jaw.  Wrenches  are  not  suitable  for  the  heavy 
general  work  of  shops,  but  are 
employed  chiefly  on  repair 
jobs  out  of  doors,  so  lessening 
the  weight  of  tools  carried, 
one  wrench  serving  for  many 
different  sizes  of  nuts. 

Among  other  lever-like 
tools  are  the  ratchet  braces 
used  for  operating  drills  by 
hand.  The  reaction  of  the 
pressure  on  the  drill  is  taken 
by  a  “John  Bull,”  which  is  a 
pillar  and  bar  rigged  up  in  any 
convenient  position.  The 
feed  is  imparted  by  a  screw, 

turned  with  a  tommy  rod,  while  the  rotation  of  the  drill  and  its 
socket  is  performed  by  the  dog  and  ratchet  mechanism,  turning 
generally  to  the  right,  d'he  objection  to  the  ordinary  ratchet  is 
that  the  drills  can  only  be  turned  in  one  direction.  To  obviate 
this  some  types  are  made  as  in  lig.  2551  double-acting,  with  a 
rocking  pawl  a,  which  can  be  thrown  over  to  work  either  to  right 


174 


TOOLS. 


or  left,  and  kept  up  by  the  spring  plunger,  which  slips  into  either 
of  the  conical  recesses  shown.  When  in  the  centre  one,  the 
ratchet  is  inoperative. 

Fig.  256  shows  the  braces  or  stocks  used  for  driving  the 
smaller  wood-boring  tools,  as  centre-bits,  shell,  and  spoon  bits, 
&c.  The  first,  a,  is  the  older  form,  very  pretty,  but  lacking  in 
range  of  utility,  and  rather  hard  to  work,  b  is  one  of  the  numerous 
improved  forms,  fitted  with  a  double-acting  ratchet,  for  working  in 
confined  situations,  and  being  provided  with  ball  bearings  in  the 
head,  the  handle,  and  the  nose. 

Another  group  of  lever  tools  is  the  tap  wrenches,  three  forms 
of  which  are  shown  in  Fig.  257.  The  first,  a,  has  but  a  limited 


range  of  capacity,  the  neck  of  the  tap  being  pinched  between  the 
vee  and  the  screwed  pin.  Other  tools,  as  reamers  and  broaches, 
can  be  held  in  this  form.  In  b,  the  jaws  and  handles  are  in 
duplicate,  fitting  with  vees,  and  the  screws  permit  of  a  wide  range 
in  the  grip  of  the  vees.  In  c  an  elastic  movement  is  provided, 
and  though  it  is  not  much  in  amount,  there  are  two  holes  avail¬ 
able.  Wrenches  such  as  these  are  better  than  the  common  solid 
hole  types,  which  become  slack,  and  pull  the  tap  necks  out  of 
shape  quickly. 

Another  very  large  group  of  tools  that  act  by  leverage  is 
represented  in  Fig.  258,  a  being  the  common  pincers,  b  the  gas 
pliers.  The  first  is  used  for  drawing  nails,  the  second  for  tighten- 


MISCELLANEOUS  TOOLS. 


175 


ing  and  loosening  the  joints  of  screwed  pipes.  In  each  case  the 
power  exercised  is  that  due  to  the  length  of  the  handles. 

Pincers  and  pliers  are  often  bad  in  the  jaws,  either  becoming 
indented  when  too  soft,  or  breaking  away  when  the  steel  facing  is 
hard,  and  imperfectly  welded  to  the  iron 
jaws.  When  purchasing  these  new,  they 
should  be  tried  on  a  tough  nail  or  two  at 
the  beginning,  and  returned  if  they  fail  to 
stand  the  test.  Some  pincers  are  made 
too  convex  on  the  face,  and  this  means  a 
loss  of  leverage,  hence  pincers  with  a  flat 
face  are  to  be  preferred. 

Allied  to  these  tools  are  the  various 
pliers,  flat,  and  round  nosed,  in  which  the 
leverage  takes  place  round  the  longitudinal 
axis.  These  are  used  for  bending  wire,  and  strips  of  sheet  metal. 
In  many,  a  chisel  tool  is  embodied  for  cutting  off  wire, — the  cut- 
ting  pliers,  or  nippers.  Pipe  wrenches  are  modified  pipe  or  gas 
tongs,  being  mostly  used  for  larger  pipes  than  the  tongs  are. 
Another  group  includes  the  tongs  used  by  smiths  and  boiler 


Fig.  259. 


makers,  three  typical  forms  of  which  are  shown  in  Fig.  259.  The 
handles  are  long  for  manipulating  forgings,  while  the  jaws  differ 
in  many  ways.  They  are  concave  in  the  direction  of  the  axis,  or 
transversely,  a.  Both  jaws  are  flat,  or  round,  equal,  or  unequal  in 
dimensions.  One  is  round,  and  other  vee’d,  b,  for  gripping  angles. 
They  are  straightforward,  or  turned-down,  as  in  the  hoop  tongs  c. 


176 


TOOLS. 


or  one  jaw  is  turned  up  on  both  sides  to  confine  work  sideways,  as 
in  the  box  tongs. 

Cramps  embrace  all  squeezing  and  gripping  tools,  from  the 
long  bar  cramps  of  the  carpenter  and  joiner,  to  the  small  finger 
cramps  used  in  light  bench  work.  The  largest  ones  will  take  in 
as  much  as  7  ft.,  which  may  be  increased  by  the  insertion  of  a 
temporary  lengthening  bar.  The  bar  a.  Fig,  260,  is  of  rectangular 
section,  made  in  wrought  iron  or  steel,  and  is  pierced  with  a 
number  of  small  holes,  pitched  at  2  or  3  in,  centres.  These 


Fig.  260, 


holes  are  for  the  insertion  of  a  pin,  attached  loosely  to  the  sliding 
head  b  of  the  cramp,  and  serve  to  fix  it  in  any  position  within  the 
range  of  the  holes,  the  pin  passing  either  through  holes  in  the 
head,  or  simply  through  the  bar  behind  the  head.  In  one 
type  of  cramp,  a  row  of  serrations  along  the  top  edge  of  the 
bar  furnishes  the  means  of  stopping  the  head,  and  the  bar  is 
not  weakened  by  being  pierced  with  holes,  though  this,  as  a 
source  of  weakness,  has  been  exaggerated,  since  the  holes  are  in 
the  neutral  axis.  At  one  end  of  the  bar  is  a  fixed  head  c,  which 


carries  a  square-threaded  screw,  the 
range  of  travel  of  which  is  about  twice 
that  of  the  centres  of  the  pin  holes  in 
the  bar.  This  screw  serves  to  push  up 
another  sliding  head  D,  which  clamps 
the  work,  A  block  of  wood  may  be 
interposed  between  the  work  and  clamp 
faces  to  prevent  injury  to  the  work  sur- 


Fig.  261. 


faces.  These  cramps  range  from  3  to  7  ft.  in  length.  Smaller 
and  lighter  ones,  called  sash  cramps,  are  made  in  sizes  below  3  ft. 

Steel  G  cramps  (Fig.  261)  are  largely  employed  by  cabinet¬ 
makers  and  carpenters,  and  in  stiffer  proportions,  by  engineers. 
Smaller  steel,  and  malleable  iron  cramps  are  very  much  used,  and 
many  of  these  for  metal  work  have  ball  heads,  which  accommodate 
themselves  to  out-of-square  faces,  instead  of  putting  a  great  strain 
on  the  screw  sideways.  Wooden  cramps  are  very  handy  where 
stuff  of  considerable  width  has  to  be  gripped.  They  are  usually 


MISCELLANEOUS  TOOLS. 


177 


cut  in  beech,  the  screws  being  formed  with  a  box  and  tap.  Many 
workmen  construct  these  themselves,  a  box  and  tap  costing  only 
a  few  shillings.  Jaws  will  range  from  6  to  14  in.  in  length. 

Screwdrivers  (Fig.  262)  or  turnscrews  differ  from  one 
another  in  length  chiefly.  The  longer  they  are,  the 
more  power  can  be  exercised  upon  them  ;  that  is  certain, 
though  it  is  not  easily  explained,  since  it  does  not  appear 
to  be  due  to  leverage.  All  screwdriver  handles  are  broad 
at  the  upper  end,  and  more  or  less  ball-like  in  form  to 
permit  of  using  them  as  levers.  The  principal  difference 
in  the  blades  is  that  between  flat  and  round.  The  latter 
are  much  to  be  preferred  because  they  will  pass  down 
into  holes  into  which  the  heads  of  screws  often  have  to 
be  sunk. 

Of  recent  years  many  useful  screwdrivers  have  been  Fig.  262. 
developed  having  a  ratchet  mechanism  embodied,  so 
that  the  hand  grips  the  handle  firmly  all  the  time,  and  the  tiring, 
and  time-wasting  shifting  of  the  hand  at  each  turn,  to  get  a  fresh 
hold,  is  done  away  with.  Engineers  use  screwdrivers  also  which 

differ  from  the  ordinary  ones,  in  having  a 
tee  or  cross  handle,  to  give  plenty  of  power, 
for  tightening  up  large  screws. 

I'he  subject  of  tool  handles  is  one  of 
much 'importance,  though  little  notice  is  ever 
taken  of  it  except  by  the  men  who  have  to 
use  them.  A  few  typical  groups  are  here 
shown.  The  forms  of  handles  vary  with 
their  functions,  being  used  for  thrusting 
straight  forward,  or  perpendicularly  by  the 
hand,  or  to  be  struck  by  the  mallet,  or  to  be 
swung  (see  Chapter  IL,  p.  30).  Obviously 
the  handle  is  a  cardinal  part  of  its  tool,  co¬ 
related  to  the  nature  of  the  work  which 
it  has  to  perform.  There  is  therefore  as 
much  variety  in  one  as  in  the  other.  When 
a  tool  is  actuated  by  pressure,  the  shape 
of  the  handle  must  be  such  as  to  offer 
resistance  to  that  pressure,  without  tiring  the  hand  greatly. 

Fig.  263  shows  a  group  of  handles  which  are  mostly  used  by 
simple  thrust  from  the  palm  of  the  hand,  or  ball  of  the  thumb. 

M 


Fig.  263. 


TOOLS. 


178 


A  is  a  bradawl  handle,  b  that  of  a  file,  c,  and  d,  for  carvers’  chisels, 
and  gouges.  In  each  of  these,  thrust  predominates,  though  occa¬ 
sionally  a  large  bradawl  is  struck  with  a  mallet,  and  carvers’  tools 
frequently  so,  or  by  the  ball  of  the  hand  used  as  a  light  mallet. 
E,  the  screwdriver  handle,  is  both  thrust,  and  turned,  hence  the 
reason  for  the  broad  end  of  the  handle,  a  and  b  are  more 
globular  in  form  at  the  end  than  c  and  D,  because  the  ball  of  the 
hand  is  always  pressing  against  the  end,  and  a  small  convexity, 
as  in  c,  would  rapidly  tire,  and  make  the  hand  sore.  Hence  a 
bradawl  handle  always  has  a  big  ball-shaped  end,  like  a  file  handle, 
in  order  not  to  tire  the  palm  of  the  hand,  and  the  ball  of  the  thumb 

by  constant  use ;  a  chisel  handle 
should,  for  the  same  reason,  be  well 
rounded  where  the  thrust  of  the  hand 
takes  place  in  horizontal  cutting  (see 
the  group  in  Fig.  264).  The  same 
well-rounded  globular  formation  next 
the  tang  affords  a  good  resistance  to 
the  pressure  of  the  hand  in  vertical 
cutting.  The  shape  of  the  inter¬ 
mediate  portion  is  of  little  moment, 
hence  we  see  it  parallel,  or  sweeped, 
or  faceted,  B,  c,  D,  in  the  kits  of  differ¬ 
ent  men,  in  Fig.  264  which  represents 
typical  handles  for  chisels,  and  gouges, 
paring  and  firmer. 

In  paring  and  firmer  chisels  the 
principal  thing  required  is  a  handle 
which  can  be  grasped  firmly,  without 
liability  of  slipping  through  the  hand.  Hence  the  swelled  portion, 
turned  with  this  view,  should  take  the  form  of  a  or  B,  rather  than 
that  of  c,  and  the  shape  of  the  upper  portion  is  of  less  importance, 
being  only  grasped  when  paring  in  a  horizontal  direction.  These 
remarks  apply  alike  to  firmer  and  paring  tools,  though  in  vertical 
paring  with  a  long  chisel  or  gouge,  it  is  usual  to  grasp  the  tool 
itself,  instead  of  the  handle,  as  being  closer  to,  and  affording  more 
control  over  the  cutting  edge.  D  is  an  old  form  for  firmer  chisels, 
little  used  now. 

The  handles  of  the  draw-knife  are  well  bellied  to  receive  the 
pull  of  the  hands. 


MISCELLANEOUS  TOOLS. 


179 


■  1 

3 

e 


In  the  mortise,  and  socket  chisels  the  shape  is  of  no  account 
from  this  point  of  view,  and  so  we  have  slightly  tapered,  or  bellied 
handles  (see  Fig.  265). 

In  mortise  and  socket  chisels  we  have  stout  handles,  too  large 
for  paring  purposes,  but  straight,  and  well  rounded  at  the  end, 
to  withstand  the  bruising  and  burr¬ 
ing  acfion  of  the  mallet. 

In  some  cases  handles  are  fitted 
with  ferrules  at  each  end,  the  usual 
one  next  the  tang  to  prevent  the  latter 
from  splitting  the  wood,  that  at  the 
opposite  end  to  prevent  the  mallet 
from  splitting  it  (Fig.  265,  A,  b). 

This  ferrule  is,  however,  awkwardly 
placed  when  using  a  chisel  by  hand 
alone,  and  it  should  therefore  be 
adopted  in  the  mortise  tools  only. 

Though  the  handles  of  most  chisels 
are  of  circular  section,  mortise 
chisels  are  a  frequent  exception, 

the  tanged  kind  being  elliptical  in  cross  section,  c,  so  that  they 
do  not  turn  about  in  the  hand.  The  handles  of  axes  and  adzes 
are  elliptical  for  the  same  reason,  to  prevent  turning  in  the 
grip.  In  all  these  matters  nothing  comes  by  chance,  but  there 
is  a  practical  reason  for  every  difference  in  detail. 

The  handles  of  turning  tools  (Fig. 
266),  are  levers  mainly,  by  which  the 
tools  are  controlled.  Long  handles  are 
necessary  to  prevent  risk  of  the  catching 
of  the  tool  points.  The  illustration 
shows  two  alternative  forms. 

Handles  of  planes  and  saws  are 
shown  in  Fig.  267,  a  being  used  for  jack 
planes  mostly,  B  for  trying  planes,  c  for  hand  saws,  and 
slightly  modified  for  tenon,  and  dovetail  saws.  Fig.  268  shows 
handles  which  have  to  be  swung  in  a  radius,  a  being  the  adze, 
B  the  axe,  and  c  the  hammer.  Variations  occur  in  these, 
especially  in  the  two  last.  Certain  proportions  are  insisted  on 
by  some  men  in  axe  handles,  particularly  those  of  the  American 
form.  Hammer  handles  vary  in  length,  from  the  bench  hammers 


Fig.  266. 


i8o 


TOOLS. 


of  from  12  in.  to  1 8  in.,  to  the  sledges  of  3  to  4  ft.  This  group 
of  handles  is  elliptical  in  cross  section,  to  prevent  turning  in  the 

hands. 

Some  men,  both  workmen  and 
amateurs,  take  great  pride  in  handles 
of  their  chisels  and  gouges,  as  for 
instance,  having  all  the  tools  in  one  set 
handled  in  one  kind  of  wood,  and 
again  in  choosing  expensive  and  fancy 
woods,  as  boxwood,  rosewood,  ebony, 
lignum  vitae,  lancewood,  snakewood, 
greenheart,  logwood,  &c.  Snakewood 
looks  very  pretty,  greenheart  and  lignum 
vitae  are  hard  to  bore,  and  brittle ;  rose¬ 
wood  is  also  brittle,  but  handsome  when  polished,  logwood  is 
open  in  the  grain ;  but  the  best  of  all  is  boxwood,  being  hard 
and  tough,  and  the  only  one  of  the  whole  which  will  stand  the 
mallet  for  any  length  of  time.  For  the  mortise  chisels,  how¬ 
ever,  nothing  beats  beech,  or  ash. 


Fig.  267. 


Fig.  268. 

Many  tools  have  no  handles,  being  struck  directly  with  mallets 
or  sledges,  or  gripped  in  the  holders  of  machines,  or  in  special 
holders,  afterwards  set  in  machines,  or,  as  in  the  moulding  planes, 
the  body  or  stock  being  grasped.  In  some  cases,  the  tools  and 
handles  are  in  one  solid  mass,  the  handle  being  formed  by  an 
extension  pf  the  shank  of  the  tool.  In  others  the  handle  is 
developed  into  a  more  elaborate  affair,  as  in  the  bow  and  hack 
saws,  where  a  strain  is  imparted  to  the  saws  by  a  cord,  or  a  screw. 


MISCELLANEOUS  TOOLS. 


i8i 


Some  tools,  like  the  cross-cut  saws,  and  the  pit  saws,  have  a 
handle  at  each  end  in  the  form  of  a  cross,  so  that  two  men 
can  operate  them.  Augers  have  cross  handles  to  afford  ample 
leverage.  The  handles  of  tools,  like  the  tools  themselves,  are  the 
result  of  a  process  of  evolution  from  periods  thousands  of  years 
distant. 


SECTION  V. 


HARDENING,  TEMPERING,  GRINDING,  AND 

SHARPENING. 

CHAPTER  XVII. 

Hardening  and  Tempering. 

Distinction  between  Hardening  and  Tempering — Method  of  Heating — 
Precautions — Methods  of  Hardening — Quenching — Drawing  Temper — 
Annealing — Mechanical  Processes. 

Hardening  and  tempering  are  two  distinct  processes. 

The  first  signifies  the  making  a  tool  intensely  hard,  the 
second  produces  a  certain  degree  of  hardness,  which 
varies  widely  in  the  case  of  tools  for  different  purposes.  Usually, 
though  not  invariably,  hardening  is  a  stage  towards  tempering, 
because  it  is  generally  easier  to  harden  first,  and  then  “  let  down,” 
for  temper,  than  it  is  to  raise  a  tool  to  the  exact  heat  required  for 
tempering.  The  latter  method  is,  however,  used  largely  when 
mechanical  aids  are  employed  for  determining  the  heat  necessary 
for  tempering.  At  the  forge  fire,  temperature  is  estimated  by  colour, 
the  principal  stages  of  which  in  the  ascending  scale  are  represented 
by  straw,  and  gold  in  various  shades,  chocolate,  or  brown,  purple, 
violet,  and  blue.  The  first  is  suitable  for  tools  of  great  hardness, 
the  last  for  springs,  or  tools  which  should  be  springy.  Researches 
into  the  chemical  characteristics  of  carbon  steel  have  not  as  yet 
been  of  much  practical  use  to  the  smith.  He  knows  that  various 
grades  of  carbon  steel  require  different  treatment,  and  that  there 
is  an  unbroken  range  of  temperature  between  blue  and  yellow 
available  for  articles  of  different  kinds.  Every  new  stock  of 
steel  which  comes  into  a  shop  has  to  be  subjected  to  its  own 
special  treatment.  If  a  new  stock,  though  of  the  same  brand, 
containing  the  same  amount  of  carbon,  and  supplied  by  the  same 


HARDENING  AND  TEMPERING. 


183 


firm,  were  treated  exactly  like  previous  stocks,  disappointment  as 
regards  hardening  and  tempering  would  almost  certainly  result. 
But  broadly,  every  brand  of  steel  is  suitable  for  special  tools,  and 
in  a  general  way  requires  the  same  kind  of  treatment. 

Steel  tools  are  heated  at  the  forge,  in  air  furnaces,  in  tubes  and 
boxes,  on  hot  plates  or  bars,  in  metallic  baths,  and  in  gas  flames. 
The  differences  between  heating  articles  simply  in  the  open  fire, 
and  in  closed  furnaces,  is  that  the  colour  test  is  adopted  in  the 
first,  and  the  thermal  test  in  the  second.  Tools  such  as  cold 
chisels,  and  those  used  for  planing,  shaping,  and  slotting,  are 
commonly  heated  in  the  open  forge  fire,  or  in  a  tube  placed  in  it, 
coal  or  coke  being  the  fuel  used.  But  milling  cutters,  drills,  taps, 
or  reamers  should  be  heated  in  a  charcoal  fire,  or  in  a  tube, 
furnace,  or  bath,  in  order  to  protect  the  tools  from  contact  with 
sulphurous  fuels,  and  uneven  temperatures.  Blast  should  not  be 
used  when  heating  steel  at  the  forge,  because  the  cold  air  is  liable 
to  warp  the  work  ;  a  hollow  fire  should  be  prepared  first,  and  the 
blast  shut  off  before  the  tools  are  introduced.  But  blast  may  be  used 
when  the  work  is  enclosed  in  a  tube.  A  tool  should  be  kept  in 
constant  movement  in  the  fire,  to  ensure  equal  heating  throughout. 
Sonking  should  not  be  prolonged  more  than  is  necessary  to  ensure 
uniform  temperature.  Steel  must  never  be  overheated,  since  it 
causes  burning,  brittleness,  and  coarseness  of  grain.  Hence  the 
invariable  rule,  always  to  harden  or  temper  at  the  lowest  heat 
which  a  given  grade  of  steel  will  take.  A  sign  of  overheating  is 
that  at  which  scale  forms  and  falls  off.  A  welding  heat  should 
never  be  reached  in  steel  tools,  the  case  of  the  high  speed  steels 
alone  excepted.  Should  the  end  of  a  tool  become  overheated, 
the  best  plan  is  to  knock  it  off,  and  reforge.  A  cherry  red  in  a 
dull  light,  say  in  the  shadow  of  the  forge,  represents  the  highest 
temperature  to  which  carbon  tool  steel  should  be  subjected. 
Scale  must  alwa5'S  be  removed  previous  to  tempering. 

When  steel  is  heated  in  furnaces,  a  sample  piece  is  first  dealt 
with  before  a  quantity  is  subjected  to  treatment.  The  advantages 
of  gas  over  solid  fuel  are  the  exact  adjustment  of  temperature  by 
means  of  valves,  its  uniformity  throughout  the  furnace,  the  non¬ 
oxidation  of  the  steel,  the  fact  that  large  numbers  of  pieces  are 
under  perfect  control,  and  to  a  large  extent  the  elimination  of  the 
personal  skill  of  the  smith.  Furnaces  are  of  especial  value  in 
heating  thick  work,  a  difficult  thing  to  do  in  a  forge  fire.  As 


184 


TOOLS. 


dimensions  increase,  the  difficulty  of  tempering  increases.  Hence 
the  trouble  which  arises  in  the  tempering  of  large  milling  cutters, 
which,  when  of  over  6  or  7  inches  diameter,  are  better  made  with 
inserted  teeth  than  out  of  the  solid.  A  similar  difficulty  occurs  in 
the  hardening  of  long  taps  and  reamers  which  warp  in  quenching, 
and  the  teeth  of  which  often  become  burnt  before  the  body  is 
saturated  throughout. 

Tempering  baths  of  molten  metal  are  composed  of  lead  and 
tin  in  varying  proportions,  different  compositions  of  which  pro¬ 
vide  a  considerable  range  of  temperatures  suitable  for  the  smaller 
tools. 

Tools  are  hardened  in  rain  water,  rather  than  in  well  water,  the 
reason  being  that  it  contains  less  lime  than  the  latter.  It  is  a 
curious  fact  that  water  which  has  been  in  use  for  a  long  time  is 
better  than  that  which  is  fresh,  hence  the  smith’s  bosh  is  seldom 
emptied,  but  only  replenished.  For  general  purposes  tepid  water 
is  preferable  to  cold,  and  the  water  soon  becomes  warm  by  the 
repeated  dipping  of  work  into  it.  Rock  salt  is  frequently  added, 
with  other  ingredients,  as  potash  and  borax,  which  are  hardening 
agents.  Other  hardening  agents  are  sal  ammoniac,  alum,  corrosive 
sublimate,  ammonia,  parings  of  horses’  hoofs,  yellow  prussiate  of 
potash,  yellow  soap,  oil,  lard,  wax,  suet,  tallow,  beeswax,  spermaceti 
oil,  pitch,  black  rosin.  Tools  can  be  made  harder  in  mercury 
than  in  any  other  liquid,  ice  or  ice-cold  water  comes  next,  or  a 
lump  of  lead,  into  which  the  points  of  small  drills  are  sometimes 
thrust  to  harden  them.  But  for  by  far  the  larger  number  of  tools, 
water,  with  or  without  some  of  the  medicaments  just  mentioned, 
is  employed. 

There  are  right  and  wrong  ways  of  quenching  tools.  7'he 
following  is  the  general  method  of  letting  down,  when  hardening 
and  tempering  are  done  in  one  operation,  or  rather  in  two 
successive  operations  at  one  heat.  The  tool  is  brought  to  a  red 
heat  two  or  three  inches  from  the  cutting  edge,  then  plunged 
vertically  into  water  for  an  instant  or  two,  so  hardening  the  surface. 
It  is  then  withdrawn,  a  portion  is  rubbed  bright  with  a  bit  of 
broken  grindstone  or  emery  wheel,  and  the  change  of  colour,  due  to 
the  heat  in  the  centre  and  shank  spreading  to  the  surface,  watched, 
until  the  colour  necessary  for  the  particular  temper  desired  appears. 
Then  it  is  dipped  in  the  water,  and  moved  about  therein  until 
cold.  The  smaller  tools  are  frequently  raised  directly  to  the 


HARDENING  AND  TEMPERING. 


185 

temperature  required  by  being  laid  on  a  bar,  one  end  of  which  is 
red  hot,  until  the  tempering  colour  appears.  When  a  heated  tool 
is  plunged  into  a  water  bosh  it  should  not  be  allowed  to  remain 
still,  but  be  moved  about  vertically.  The  reason  is  that  the  water 
in  immediate  contact  with .  the  hot  steel  becomes  converted  into 
the  spheroidal  state,  each  globule  being  surrounded  by  a  film  of 
steam,  which  delays  the  hardening  process.  Movement  of  the 
work  brings  it  into  contact  with  cooler  water.  This  explains  why 
mercury,  which  does  not  volatilise  at  the  temperature  for  hardening 
steel,  is  the  most  perfect  hardening  agent. 

The  high  speed  steels  are  not  quenched  in  water,  but  in  air, 
either  in  still  air,  or  in  a  blast.  They  are  not  tempered,  but 
hardened,  being  heated  until  the  tips  of  the  tools  begin  to  melt. 
These,  however,  are  not  carbon  steels,  but  owe  their  hardness  to 
tungsten,  molybdenum,  &c. 

The  question  of  hardening  and  tempering  is  a  wide  subject, 
which  can  only  be  touched  on  lightly  in  a  volume  of  this  char¬ 
acter.  A  few  remarks  on  different  tools  will  therefore  conclude 
this  section.  Taps  and  reamers  are  not  let  down  in  the  same 
way  that  chisels  are.  They  are  hardened  first,  and  then  reheated 
for  temper.  It  is  usual  to  cover  the  teeth  to  lessen  risk  of 
cracking — oil,  flour  paste,  or  soap  and  oil,  or  yeast  are  used  for  this 
purpose.  They  are  generally  enclosed  in  a  tube  in  the  fire,  the 
lower  end  being  plugged 'up.  Or  if  produced  in  quantity,  they 
are  heated  in  a  box  of  charcoal  powder,  placed  in  a  furnace.  The 
water  for  quenching  should  have  a  temperature  of  about  80°. 
The  colour  should  be  a  light  straw,  and  the  square  necks  a  blue. 
Such  tools  should  always  be  plunged  vertically,  to  lessen  risk  of 
w.irping.  Dies  are  heated  to  a  cherry  red,  and  hardened  in  raw 
linseed  oil.  They  are  reheated  to  a  medium  straw,  and  quenched. 
Hobs  and  milling  cutters  are  frequently  heated  in  a  box  in  char¬ 
coal  powder,  hardened,  and  then  tempered  in  water  at  80°,  to 
which  soft  soap  is  often  added.  Punches  are  tempered  at  a 
brown,  or  a  dark  blue.  Thin  pieces  of  steel,  such  as  knife  blades, 
are  frequently  tempered  between  stout  plates  of  iron,  to  prevent 
risk  of  warping. 

When  hardened  tools  require  to  be  recut,  the  temper  has  to 
be  drawn,  preparatory  to  recutting.  To  draw  the  temper  of  tools, 
place  them  within  a  tube  made  hot  in  the  fire.  They  may  be 
then  allowed  to  cool  slowly  in  sawdust  or  wood  ashes,  or  in 


i86 


TOOLS. 


powdered  charcoal.  Another  operation  which  is  often  performed, 
is  the  annealing  of  steel,  preparatory  to  hardening  and  tempering. 
Its  object  is,  to  lessen  the  risk  of  distortion,  and  cracking.  It  is 
of  especial  value  in  such  tools  as  milling  cutters,  taps,  reamers, 
which  are  peculiarly  liable  to  go  out  of  truth.  It  is  effected  in 
the  same  manner  as  drawing  the  temper,  heating  slowly,  and 
cooling  down  in  the  above-mentioned  substances. 

The  foregoing  remarks  refer  chiefly  to  work  done  by  the 
smith  at  the  forge,  but  in  large  manufacturing  processes  the 
occupation  of  the  smith  is  gone,  displaced  by  semi-automatic 
mechanism.  In  some  cases  the  articles  are  carried  through  the 
furnace  by  mechanism,  becoming  heated  during  their  passage, 
and  discharged  automatically  into  the  cooling  bath,  articles  with 
holes  are  stuck  on  pins  standing  out  from  an  endless  chain,  that 
passes  into  the  furnace  at  one  end,  and  out  over  the  hardening 
bath  at  the  other.  Sometimes  small  pieces  are  laid  on  trays, 
which  rotate  horizontally  in  the  furnace,  or  they  are  carried 
through  on  an  iron  link  belt.  In  continuous  heating  furnaces, 
the  hardening  bath  is  maintained  at  a  constant  temperature ;  in 
some  cases,  the  hot  liquid  is  drawn  from  the  top,  run  down 
through  pipes,  and  pumped  back  when  cooled.  Or  the  tank  is 
jacketed  with  cold  water,  circulating  around  it  at  a  suitable  rate  ; 
in  others,  ice  is  employed  for  keeping  the  temperature  down. 


CHAPTER  XVIII. 


Tool  Grinding  and  Sharpening. 

Hand  Grinding — Variable  Results  of— Mechanical  Grinding — Due  largely  to 
Emery  Wheels — Precision  of — Natural  Grindstones — Lack  of  Homo¬ 
geneity — Composition — Hardness  and  Softness — Glazing — Truing — Double 
Grindstone  —  Speeds  of  Running  —  Mounting  — ■  Water  —  Comparison 
between  Grindstones  and  Emery  Wheels — Grading — Speeds  of — Truing — 
Forms  of  Wheels — Wet  Grinding — Tool  Grinding — ^Tool  Grinders — Ex¬ 
amples  of,  for  Hand  Grinding — Grinding  Woodworkers’  Tools  by  Hand — 
Plane  Irons — Gouges — Sharpening — Wire  Edge — Errors  in  Practice — 
Gouge  Slips — Mechanical  Grinding — Examples  of  Machines  for  Single- 
edged  Tools— Sharpening  Reamers — Milling  Cutters,  &c. 

OOL  grinding  is  a  wide  subject  in  regard  to  the  classes  of  work 
I  done,  and  the  methods  by  which  they  are  accomplished, 
and  there  is  a  corresponding  variation  in  the  grinding 
machines  adapted  to,  or  constructed  for  the  purpose. 

In  all  grinding,  a  movement  of  the  tool  relatively  to  the  wheel 
is  either  essential  or  desirable.  It  is  essential  when  broad  facets 
are  being  ground,  in  order  to  prevent  glazing  of  the  wheel,  because 
moving  the  work  permits  the  swarf  to  get  away.  It  is  desirable  as 
a  means  of  preservation  of  the  truth  of  the  wheel,  a  traversing 
movement  of  the  tool  wearing  it  away  equally,  instead  of  cutting  it 
into  grooves. 

In  a  large  number  of  shops  to-day — as  in  all  until  a’  few  years 
ago — tool  grinding  is  commonly  done  by  hand,  without  any  assist¬ 
ance  from  mechanical  aids.  The  custom  then  was,  and  is  still,  to 
bridge  the  trough  just  in  front  of  the  stone  with  a  piece  of  square 
bar,  and  to  use  this  as  a  rest  upon  which  to  lay  the  tool  during 
grinding.  As  the  stone  becomes  worn  down,  the  bar  is  set  along 
to  follow  it.  The  tools  for  lathe,  planer,  shaper,  slotter,  and  drilling 
machine  are  thus  ground  without  any  further  aid,  being  held  in, 
and  manipulated  by  the  hands.  The  ends  or  faces  of  the  tools 
are  held  against  the  stone,  the  latter  revolving  towards  the  work- 


i88 


TOOLS. 


man,  so  imparting  the  front  rake.  The  top  rake  is  imparted  by 
laying  the  tool  on  its  side  against  one  edge  of  the  stone.  What¬ 
ever  angle,  and  whatever  profile  is  wanted,  is  produced  by  giving 
the  requisite  inclination  to  the  tool  in  relation  to  the  stone,  and  by 
moving  it,  or  holding  it  rigidly,  according  to  the  shape  wanted  in 
plan,  whether  a  straight,  or  a  curved  face,  &c.  In  order  to  main¬ 
tain  something  like  uniformity  of  cutting  angles,  gauges  of  sheet 
metal  having  certain  angles  filed  in  them  are  sometimes  kept  by  the 
men,  both  for  use  with  common  tools,  and  with  drills.  Actually 
very  great  variations  are  found  in  tools  in  a  shop  where  this  system 
prevails,  even  for  those  doing  the  same  class  of  work,  in  nominally 
the  same  class  of  metals. 

This  system  has  been  abandoned  in  those  shops  which  have 
endeavoured  to  bring  themselves  into  line  with  modern  require¬ 
ments.  There  are  obvious  objections  to  it,  partly  by  reason  of  the 
waste  of  time  which  it  involves,  and  partly  because  it  is  a  loose 
kind  of  practice,  in  which  every  man  does  that  which  seems  right 
in  his  own  eyes,  too  often  without  much  basis  of  common-sense 
in  regard  to  the  appreciation  of  the  conditions  which  underlie  the 
action  of  cutting  tools.  In  a  few  cases  there  might  be  some 
advantage  in  the  system,  as,  when  a  man  by  long  experience  has 
learned  how  best  to  vary  the  angles  and  the  shapes  of  the  cutting 
edges  of  tools,  so  that  they  shall  operate  with  the  highest  eflfi- 
ciency  on  different  grades  of  metals  and  alloys.  It  is  well  known 
that  men  hold  different  opinions  as  to  the  best  shapes  to  give  to 
tools  for  certain  purposes.  But  the  waste  and  loss,  and  generally 
the  poor  results  of  the  system  have  condemned  it  in  the  best 
practice,  and  its  place  is  taken  by  mechanical  systems  of  grinding 
involving  a  series  of  uniform  angles  for  tools  which  operate  on 
similar  materials,  and  in  some  instances,  as  a  matter  of  convenience, 
uniform  angles  for  materials  which  are,  in  some  degree  at  least, 
dissimilar  in  physical  characteristics.  The  system  is  still  retained 
extensively,  being  only  p.irtially  displaced  by  the  later  one  of 
greater  precision.  But  in  numerous  instances  the  emery  wheel 
has  taken  the  place  of  the  grindstone,  and  is  fitted  up  with  rests 
of  tee  or  other  shapes,  in  which  more  care  is  taken  of  the  design 
than  of  old. 

It  is  largely  due  to  the  emery  wheel  that  a  better  shop  system 
has  been  introduced  than  that  which  prevailed  before.  It  was 
formerly  thought  that  only  stones,  either  natural  or  artificial. 


TOOL  GRINDING  AND  SHARPENING.  189 


were  suitable  for  tool  grinding,  because  the  tools  could  be  then 
kept  cool  by  the  application  of  water.  But  since  emery  wheels 
have  been  rendered  insoluble  in  water,  the  conditions  have  become 
changed.  And  of  late  years  wheels  of  corundum,  and  those  of 
carborundum — a  product  of  the  electric  furnace — have  entered 
into  rivalry  with  emery.  Carborundum  is  a  more  durable 
material.  Instead  of  each  man  now  going  to  the  stone  to  grind 
his  own  tools  according  to  his  taste  and  fancy,  they  are  done  in 
batches  in  the  toolroom  to  uniform  angles,  so  that  all  over  the 
shop,  tools  which  have  to  do  the  same  class  of  work  are  ground 
precisely  alike,  and  the  lathe,  planer,  or  shaper  is  not  left  standing 
idle,  in  consequence  of  the  attendant  being  always  at  the  stone 
waiting  his  turn,  or  spinning  a  quiet  yarn  with  a  mate.  The 
more  precise  the  work  done  by  the  tools,  the  more  need  is  there 
of  having  emery  wheels  fitted  up  with  suitable  rests,  or  holders, 
and  provision  for  setting  to  the  exact  angles  which  have  been 
predetermined  on  as  the  best.  There  is  then  no  guess  and  trial, 
no  setting  and  checking,  but  the  tool  can  be  put  in  its  rest,  or  box 
at  once,  and  started  to  work.  As  the  emery  wheels  are  run  at 
higher  speeds  than  stones,  they  are  protected  with  hoods,  which  in 
some  tool-grinding  machines  cover  the  upper  part  of  the  wheel 
only,  so  that  both  sides  of  the  latter  can  be  used.  The  water,  too, 
instead  of  being  dropped  or  poured  over  the  wheel  from  above, 
and  gathering  centrifugal  force  with  the  wheel,  with  excessive 
splashing,  is  directed  exactly  at  the  grinding  zone,  and  is  confined 
to  that  area  by  means  of  broad  plates  of  metal. 

Natural  grindstones  are  obtained  from  the  millstone  grit,  a 
Carboniferous  formation.  They  are  largely  quarried  in  Derbyshire, 
near  Rowsley,  and  Stanton,  and  at  Hardsley,  and  Wickersley, 
situated  a  few  miles  distant  from  Sheffield.  These  are  hard  and 
coarse  stones,  suitable  for  heavy  work.  Bilston  stones  are  used 
for  fine  cutlers’  work,  as  also  are  the  Sheffield  bluestones,  found 
close  to  the  town.  But  the  largest  proportion  of  grindstones  used 
in  this  country  come  from  the  Newcastle  district,  from  the  quarries 
of  Messrs  Kell  &  Co.,  R.  Pattison  &  Son,  and  R.  Robson. 
They  are  of  a  natural  siliceous  sandstone,  which  has  been  quarried 
for  more  than  a  hundred  years  for  the  purpose.  Stones  as  large 
as  8  ft.  in  diameter,  by  from  12  in.  to  16  in.  thick,  are  supplied  by 
these  firms. 

The  chief  trouble  in  a  natural  stone  is  lack  of  homogeneity. 


igo 


TOOLS. 


and  the  larger  the  stone,  the  more  difficult  is  it  to  secure  freedom 
from  the  presence  of  fossils,  particles  of  iron,  and  seams.  The 
presence  of  seams,  however  minute,  is  fatal  to  the  safety  of  a  stone 
revolving  at  a  high  speed,  and  it  is  not  always  easy  to  detect  these 
when  of  slight  dimensions.  As  a  stone  becomes  reduced  in  dia¬ 
meter,  in  consequence  of  wear,  the  speed  has  to  be  increased,  and 
in  this  way  a  stone  is  often  more  liable  to  fracture  after  having 
been  in  use  for  some  time  than  when  first  hung.  In  order  to 
diminish  the  risks  of  seams  or  flaws  developing,  it  is  the  practice 
to  rough-hew  the  stones  when  fresh  from  the  quarry,  and  then  lay 
them  aside  for  a  while  to  dry,  and  harden,  when  there  is  a  greater 
chance  of  flaws  becoming  visible. 

Other  properties  besides  homogeneity  are  requisite,  as  relative 
hardness  or  softness,  fineness  or  coarseness  of  grain,  rapidity  or 
otherwise  of  cutting,  the  general  texture  of  the  particles,  whether 
smooth,  or  angular  and  sharp.  Hence  when  ordering  a  grindstone 
it  is  necessary  to  state  the  exact  purpose  for  which  it  is  to  be  used. 
It  is  because  of  unsuitable  selection  having  been  made  that  com¬ 
plaint  is  frequent  of  glazing,  though  this  is  often  due  to  running  at 
too  high  a  speed.  The  texture  of  stones  varies  widely,  ranging 
from  grains  of  almost  microscopic  minuteness,  to  those  of  about 
the  size  of  a  pea.  Such  being  the  case,  it  is  possible  to  obtain 
any  quality  desired  for  quick  or  slow  cutting,  for  fine  or  coarse 
finish.  The  best  stones  show  so  little  grain,  or  traces  of  strati¬ 
fication  that  it  is  often  difficult  to  detect  it. 

Silica  is  the  principal  element  in  natural  grindstones,  amount¬ 
ing  to  more  than  8o  per  cent.  It  acts  as  a  cementing  material,  in 
common  with  carbonate  of  lime,  and  oxide  of  iron.  On  the  due 
proportioning  of  these  elements  the  texture  of  a  stone  largely 
depends.  Silica  in  excess  produces  extreme  hardness ;  much  car¬ 
bonate  of  lime,  and  iron  oxide  render  stones  too  soft  for  grinding 
purposes.  What  is  termed  grey  grit  ”  is  that  suitable  for  grinding 
engineers’  tools. 

Hardness  and  softness  are  relative  terms  in  speaking  of  grind 
stones,  these  qualities  depending  on  degrees  of  coarseness  or 
fineness,  as  well  as  on  absolute  hardness  or  softness.  A  fine  grit 
stone  may  be  softer  than  a  coarse  grit  one,  and  yet  operate  as 
though  harder,  because  of  the  slower  action  of  its  particles.  A 
hard  stone  is  of  little  value  for  engineers’  general  use,  because  it 
acts  too  slowly,  and  becomes  glazed  quickly.  In  a  soft  stone  the 


TOOL  GRINDING  AND  SHARPENING.  191 

particles  cut  rapidly,  and  are  themselves  abraded,  exposing  a  fresh 
layer  beneath.  The  water  also  penetrates  more  readily  between 
the  particles,  and  washes  away  the  swarf  before  it  can  become 
embedded  in  the  stone,  and  so  carries  off  the  heat  generated  in 
grinding. 

When  the  surface  of  a  stone  becomes  glazed,  it  must  be  turned 
down,  since  the  gritty  particles  offer  no  projecting  points  for  action. 
A  stone  that  glazes  quickly  is  of  no  use,  because  of  the  cost  of 
keeping  it  in  order,  and  the  waste  of  time  involved  in  the  slowness 
of  its  operations.  The  writer  has  read  of  granite  bearimgs  being 
sometimes  used  for  water  wheels  in  Sweden,  because  of  the  perfect 
manner  in  which  they  glaze,  becoming  like  metallic  surfaces.  If 
a  stone  is  too  soft,  there  is  the  evil  of  too  rapid  wear,  and  cost  for 
renewal.  Some  soft  stones  cut  rapidly,  others  are  so  soft  as  to 
be  nearly  useless. 

Grindstones  are  trued  with  a  pointed  bar  of  iron  or  steel,  or 
with  the  end  of  a  piece  of  gas  pipe,  or  with  a  special  appliance 
termed  a  “  grindstone  truer,”  of  which  there  are  two  or  three  types, 
and  by  which  the  operation  is  facilitated. 

To  turn  a  grindstone  with  a  pointed  bar  or  a  tube,  it  is  revolved 
at  a  slow  speed — not  more  than  eighty  or  ninety  revolutions  per 
'  minute, — and  is  run  dry.  The  bar  taken  is  about  ^  in.  or  f  in. 
square,  and  is  of  iron  or  steel — it  does  not  matter  which,  because 
the  bar  loses  its  keen  edge  instantly,  and  its  effective  action 
depends  on  the  constant  and  rapid  change  of  position  by  which 
fresh  facets  are  applied  to  the  stone.  The  bar,  therefore,  is  kept 
in  continual  motion,  being  rotated  on  its  own  axis — presented  at 
slightly  different  angles — and  traversed  across  the  stone  at  one  and 
the  same  time.  It  is  held  at  a  vertical  angle,  constantly  varying, 
but  averaging  somewhere  about  15°  to  20°. 

When  a  stone  is  newly  turned  its  surface  is  finished  to  a  slight 
convexity,  because  all  shop  stones  tend  to  wear  hollow,  by  reason 
of  the  grinding  being  done  less,  at,  and  near  the  edges  than  about 
the  centre.  The  narrow  tools  of  the  machinist,  and  the  gouges  of 
the  patternmakers,  and  joiners  soon  wear  concavities.  The  edges 
of  the  stone  should  also  be  trued  for  an  inch  or  two  downwards, 
because  it  is  often  necessary  to  use  these  edges  in  grinding. 

Muir’s  double  grindstone  is  designed  with  a  view  to  obviate 
the  necessity  of  frequent  retruing.  T.  wo  stones  are  run  edge 
to  edge,  with  adjustable  centres,  and  men  can  work  at  each. 


192 


TOOLS. 


The  stones  keep  one  another  true  by  the  slight  contact  which 
takes  place. 

It  is  not  easy  to  say  at  what  speed  grindstones  should  be  run. 
We  perhaps  err  on  the  side  of  extreme  slowness  ;  the  Americans  go 
to  the  other  extreme,  running  their  stones  at  rates  perilously  near 
to  the  bursting  point.  We  make  a  great  difference  in  the  speeds 
of  grindstones,  and  of  emery  wheels  ;  they  think  no  such  differences 
should  exist.  Since  time  is  money,  they  run  the  stones  to  their 
utmost  limit.  In  some  American  shops  the  grinders  have  a  very 
matter-of-fact  way  of  ascertaining  the  highest  speed  at  which  it  is 
safe  to  run  them.  They  test  the  stones  at  a  rate  rather  higher  than 
the  highest  which  experience  tells  them  is  desirable,  and  then  if 
they  stand  it  they  use  them  at  a  speed  a  trifle  below.  Stones  there 
are  commonly  run  at  peripheral  rates  of  between  4,000  and 
5,000  ft.  per  minute. 

The  peripheral  speed  of  a  stone  in  English  machine  shops  used 
for  grinding  tools  probably  ranges  only  from  about  800  to  1,200  ft. 
per  minute,  or  in  the  case  of  a  stone  of  3  to  4  ft.  diameter  from  90  to 
100  revolutions  per  minute;  being  therefore  the  same  s[)eed  as  slow 
main-line  shafting,  it  is  run  by  pulleys  of  about  equal  diameter  on 
shaft  and  stone.  It  is  not  necessarily  supplied  with  fast  and  loose 
pulleys,  because  it  is  kept  running  all  the  while  for  constant  service, 
which  is  better  also  than  allowing  it  to  stand  in  the  water.  As 
stones  wear  down,  the  speed,  of  course,  should  be  increased.  But 
the  usual  practice  in  shops  is  not  to  alter  the  speed,  but  to  replace 
the  stone  with  a  new  one  before  it  wears  very  small — that  is,  when 
a  3  ft.  stone  wears  down  to,  say,  2  ft.,  it  is  taken  out,  and  the  2  ft. 
stone  finds  a  place  elsewhere. 

There  are  two  methods  of  mounting  grindstones.  One  way  is 
to  have  a  square  hole  in  the  centre  of  the  stone,  into  which  a 
square  axle,  measuring  across  the  flat  from  f  to  |  in.  less  than  the 
hole,  and  having  the  ends  turned  down  to  form  suitable  journals, 
is  fitted  tightly  with  wedges  of  hard  wood.  The  operation  is 
termed  “hanging  the  stone,”  probably  from  the  fact  that  during 
the  fitting  of  the  wedges,  the  adjustments  are  made  by  turning  the 
stone  from  time  to  time  until  that  degree  of  correction  effected  by 
the  wedges  is  reached  at  which  the  stone  runs  true.  Once  the 
wedges  are  adjusted  and  driven  tightly  they  seldom  work  loose, 
because  the  water  keeps  them  in  a  swollen  condition.  This  is  the 
old  millwright’s  way,  and  for  grindstones  it  is  as  good  as  the  alter- 


TOOL  GRINDING  AND  SHARPENING.  193 


native  fashion  of  having  a  round  hole,  round  axle,  and  side 
clamping  plates. 

Water  is  generally  fed  on  the  grindstone  from  a  can  fixed  over 
it.  The  tap  is  turned  to  allow  the  water  to  drip  slowly  without 
causing  it  to  be  unnecessarily  thrown  off,  and  splashed.  The 
custom  of  partly  filling  the  trough  with  water,  and  allowing  the 
stone  to  run  in  it  causes  much  mess  ;  while  keeping  the  water 
below  the  stone,  and  splashing  up  small  quantities  with  a  flat  piece 
of  wood,  is  a  clumsy  and  disagreeable  practice. 

In  the  commonest  method  of  watering  a  stone  by  letting  the 
water  run  down  from  the  spout  of  a  drip-can,  keeping  the  tool  to 
be  ground  in  the  vicinity  of  the  dropping  water,  there  is-  no  distri¬ 
bution  of  the  water  over  the  breadth  of  the  stone.  A  frequent 
practice,  therefore,  is  to  let  the  water  fall  on  to  a  piece  of  cloth 
suspended  from  the  drip-can  stand,  and  lying  across  the  stone  a 
few  inches  higher  than  the  area  where  the  grinding  is  done.  The 
water  is  then  distributed  over  the  whole  breadth  of  the  stone 
evenly,  and  without  splashing  occurring. 

The  grindstone  consists  of  a  multitude  of  sharp  cutting  points 
held  together  with  a  cementing  materal.  As  the  particles  become 
abraded,  the  cementing  material  is  also  softened,  or  dissolved,  and 
removed.  The  water  used  dissolves  the  cement.  Hence  the 
reason  why  stones  which  stand  in  water  become  softened  in  that 
part  which  is  in  the  water.  It  was  by  an  application  of  this 
principle  that  Poole’s  wheels  for  calender  rollers  were  made. 
They  were  of  emery,  cemented  with  substances  soluble  in  soda 
water.  The  wheels  being  kept  wet  with  an  alkaline  solution,  the 
cementing  material  on  the  surface  became  dissolved,  and  fresh 
grinding  surfaces  were  continually  presented  to  the  work. 

Probably  the  capacity  of  the  common  grindstone  has  never 
been  developed  as  it  might  have  been  in  engineers’  shops.  That 
of  the  emery  wheel  has,  and  therefore  comparisons  between  the 
two  have  not  been  made  under  the  same  conditions.  To-day  the 
grindstone  is  considered  an  antiquated,  and  is  often  an  ill-used 
piece  of  mechanism.  Sometimes  selected  without  regard  to  its 
requirements,  it  is  too  soft,  or  too  hard  for  its  purpose;  or  it  is 
not  homogeneous,  and  consequently  wears  unequally.  It  is 
allowed  to  stand  partly  immersed  in  water,  so  softening  it  locally. 
It  is  used  so  badly  that  it  loses  its  circular  form,  and  becomes  cut 
into  grooves  so  that  accurate  work  is  impossible.  Nobody  is  re- 

N 


194 


TOOLS, 


sponsible  for  it,  and  only  when  it  becomes  scored  very  badly,  a 
shop  labourer  turns  it  up.  It  is  nearly  always  run  at  too  slow  a 
speed — at  a  mere  crawling  pace.  Such  are  the  conditions  under 
which  it  exists  in  many  shops  to-day. 

With  emery  wheels  different  conditions  exist.  They  are  gene¬ 
rally  homogeneous,  and  their  grades  are  regulated  with  more  or 
less  care,  according  to  the  special  work  they  have  to  do.  They 
are  fitted  up  with  suitable  bearings,  their  speeds  regulated  by  the 
manufacturers,  and  the  general  conditions  under  which  they  must 
be  employed  are  insisted  on.  Generally,  they  are  used  by  the 
regular  grinders  only,  part  of  whose  business  is  to  keep  the  wheels 
true,  and  in  good  general  order.  If  the  same  care  and  attention 
had  been  given  to  the  grindstones  as  to  the  emery  wheels,  it  is 
probable  they  would  not  have  been  displaced  to  the  extent  to 
which  they  have  been. 

Emery  wheels  are  graded  by  coarseness  or  fineness,  and  by 
softness  or  hardness.  The  first  are  known  by  numbers,  the  second 
by  letters.  Between  the  extreme  range  in  each  lie  all  shades  of 
difference,  and  in  this  fine  graduation  lies  one  of  the  chief  ad¬ 
vantages  of  the  emery  wheels  over  the  grindstones.  Besides  these, 
other  governing  conditions  come  in  to  supplement,  and  influence 
the  selection  of  wheels,  such  as  the  width  of  wheel  and  width  of 
work,  the  nature  of  the  material  being  ground,  and  the  speed — 
matters  the  settlement  of  which  being  to  some  extent  mutually 
dependent,  require  considerable  experience  in  the  work  of  grinding. 

As  very  general  rules  only,  subject  to  the  usual  exceptions, 
soft  wheels  cause  less  change  of  temperature  in  the  work,  and 
glaze  less  than  hard  ones.  Coarse,  soft  wheels  can  be  run  at 
higher  speeds  than  fine,  hard  ones.  Having  a  wide  surface  of  the 
work  and  wheel  in  contact,  the  wheel  should  be  softer  than  for 
narrower  surfaces.  But  it  is  well  to  use  a  wheel  of  the  fullest 
width  practicable.  The  use  of  water  is  serviceable  in  preventing 
changes  of  temperature,  which  would  draw  the  temper  in  cutting 
tools.  The  best  wheels  are  those  which  contain  least  cementing 
material  and  most  emery,  or  which  contain  a  cementing  material 
having  cutting  qualities  similar  to  the  emery. 

There  is  much  variation  in  the  speeds  of  emery  wheels,  ranging 
from  about  4,500  to  6,000  ft.  per  minute  peripheral  speed.  About 
5,500  ft.  seems  to  be  the  most  suitable  from  the  point  of  view  of 
practical  efficiency.  The  faster  a  wheel  revolves,  the  quicker  will 


TOOL  GRINDING  AND  SHARPENING. 


195 

it  cut,  but  the  more  rapidly,  too,  will  it  become  worn  out.  Exact 
experiment  has  borne  out  common  knowledge  that  high  speeds  are 
the  most  economical. 

It  is  even  more  necessary  to  true  an  emery  wheel  when  it  has 
worn  slightly  out  of  truth,  than  a  grindstone,  because  of  the  differ¬ 
ence  in  speed,  the  rapidly  revolving  emery  wheel  when  out  of 
balance  being  more  liable  to  fly  asunder  than  the  stone.  Emery 
wheel  dressers  are  supplied  of  the  circular  type,  held  in  the  slide 
rest  similarly  to  a  knurling  tool  for  milling  the  edges  of  the  heads 
of  binding  and  micrometer  screws,  &c.  The  edges  of  the  circular 
cutters  are  pointed  like  saw  teeth,  and  they  reduce  the  emery  by 
hacking  out  the  grains.  The  wheel  must  be  revolved  slowly,  at 
a  peripheral  speed  of  80  to  100  ft.  a  minute  only,  and  the  cutting 
must  be  light.  The  dressing  must  be  done  from  the  edges  towards 
the  centre  to  prevent  risk  of  the  edges  breaking  away.  In  turning 
down  emery  wheels  to  sectional  forms  the  best  plan  is  to  use  a 
black  diamond  held  in  a  slide  rest,  taking  light  cuts,  as  the  dia¬ 
mond  is  very  brittle.  These  are  rather  costly,  and  therefore  plain 
and  heavy  wheels  that  have  not  to  be  turned  to  sectional  forms  are 
often  turned  by  cross-hatching  them  first,  similarly  to  grindstones, 
and  then  turning  the  chipped  surface  with  the  jagged  edge  of  a 
piece  of  boiler  plate  that  has  been  punched  or  shorn  to  outline. 
Or  the  wheel  dressers  just^  mentioned  are  employed ;  and  this  is 
much  the  better  way. 

Emery  wheels  are  either  discs,  rings,  or  cylinders,  and  they 
are  plain,  or  of  numerous  sectional  shapes  to  suit  special  work. 
Discs  are  the  most  common,  being  employed  for  general  purposes 
of  all  kinds.  Rings  are  used  to  save  the  waste  of  the  central  part 
of  a  solid  wheel,  which,  when  the  wheel  is  worn  down,  becomes  too 
small  to  be  of  any  further  service.  With  the  cylindrical  wheel, 
work  is  ground  on  the  face,  and  no  alteration  of  speed  due  to  wear 
is  necessary,  because  there  is  no  reduction  in  diameter. 

The  practice  of  wet  grinding,  which  is  a  secondary  develop¬ 
ment  in  the  use  of  emery  wheels,  has  attained  an  importance  equal 
to  that  of  the  original  dry  grinding.  Tools  are  ground  thus,  and 
also  work,  in  which  a  rise  of  temperature  would  be  objectionable 
as  affecting  dimensions.  The  designs  of  wet  grinders  therefore  are 
very  numerous,  and  have  attained  a  high  degree  of  excellence. 

Water-trough  tool  grinders,  it  may  be  mentioned,  should  be  fitted 
with  a  door  near  the  bottom  to  permit  of  clearing  out.  In  some 


196 


TOOLS. 


machines  of  the  floor  stand  type,  in  which  the  base  serves  as  a 
water  tank,  fitted  with  centrifugal  pump  and  adjustable  water  pipe, 
the  hood  is  made  with  an  opening,  and  a  planed  top.  Consequently, 
flat  surfaces  can  be  ground  on  this,  besides  the  tool  grinding  that 
is  done  at  the  front.  When  flat  grinding  is  not  being  performed, 
the  opening  is  closed  with  a  cover. 

In  one  good  and  common  tool  grinder  a  trough  of  semicircular 
outline  in  front  serves  as  a  water  pan,  this  outline  permitting  the 
workman  to  get  round  easily  to  either  side  of  the  wheel.  Adjust¬ 
able  guards  prevent  the  spray  from  flying  about  over  the  man  and 
the  surrounding  objects.  The  tool  rests  are  moved  back  as  the 
wheels  wear  down,  and  the  use  of  gun-metal  bolts  prevents  rusting 

up.  The  water  supply  is  adjusted 
exactly  as  wanted  by  means  of  a 
hand  wheel,  and  once  adjusted,  the 
supply  remains  constant.  The 
wheels  are  kept  true  by  turning  a 
hand  wheel,  without  removing  any 
parts.  Tool  grinders  of  this  kind 
are  made  either  single  or  duplicated 
on  one  stand. 

In  the  Barnes  grinder  (Fig.  269) 
the  supply  of  water  is  regulated  by  a 
treadle.  The  front  portion  of  the 
grinder  is  a  hollow  standard  con¬ 
taining  the  water,  in  which  there  is 
a  float  B  nearly  filling  the  column. 
The  workman,  when  about  to  start 
grinding,  simply  steps  on  the  treadle,  which  pulls  the  float  down 
into  the  water,  causing  the  latter  to  rise  round  the  wheel.  Re¬ 
leasing  the  foot,  the  float  rises  and  the  water  falls  back. 

When  the  float  is  pressed  down,  the  water  passes  slowly  through 
a  small  hole  in  a  partition  that  separates  the  pillar  from  the 
trough,  and  is  carried  up  round  the  wheel  to  the  upper  front  part, 
where  it  enters  a  chamber  opening  on  the  wheel  just  above  the 
tool  to  be  ground.  This  permits  of  a  regular  and  moderate  flow 
of  water  just  where  it  is  wanted  without  unduly  flooding  the  wheel. 
In  the  Gould  &  Eberhardt  tool  grinder  the  water  is  supplied  to 
the  wheel  by  a  pump  at  the  side  of  the  machine. 

Small  bench  emery  wheels  are  fitted  for  wet  grinding  of  tools. 


Fig.  269. 


TOOL  GRINDING  AND  SHARPENING. 


197 


The  peripheral  speed  is  less  than  half  that  used  for  dry  grinding 
for  general  purposes,  being  at  the  rate  of  about  1,800  ft.  per  minute. 
Such  machines  can  be  located  about  a  shop  where  the  men  do 
their  own  grinding.  The  wheel  is  covered  by  a  hood  except  where 
grinding  is  being  done. 

The  tool  grinder  of  the  Leland  &  Faulconer  Company  (Fig. 
270)  includes  several  devices  of  an  interesting  and  practical 
character.  The  tool  that  is  being  ground  is  laid  upon  a  rest  which 


A 


Fig.  270, 


is  protected  by  a  counterbalanced  guard  from  the  splashing  of 
water,  the  guard  rising  up  over  the  face  of  the  wheel  when  the 
latter  is  not  in  use.  The  truth  of  the  wheel  is  maintained  with 
frequent  dressing  by  means  of  a  truer  that  Is  always  kept  close  to 
the  wheel  at  the  front.  This  is  a  threaded  roll  of  steel,  which  is 
pressed  into  light  contact  with  the  wheel  for  a  few  minutes  each 
day  by  turning  the  knob  a  above.  The  supply  of  water  is  re¬ 
gulated  by  means  of  a  hinged  pan  b  within  the  main  trough,  the 


198 


TOOLS. 


latter  containing  a  constant  supply  of  water,  the  former  a  variable 
volume  which  is  graduated  at  the  will  of  the  attendant  by  means 
of  a  small  hand-wheel  c  that,  moving  a  lever,  depresses  the  front 
end  of  the  pan.  The  amount  of  depression  regulates  the  entering 
volume  of  water.  The  pan  is  balanced.  The  water  is  carried 
round  the  wheel  and  distributed  through  the  passage  d  in  the  face 
and  through  tubes  e  at  the  sides. 

In  a  tool  grinder  by  the  Whitney  Manufacturing  Company,  of 
Hartford,  the  supply  of  water  is  regulated  by  means  of  a  handle  at 
the  side,  slipping  into  a  number  of  notches  in  a  quadrant,  in  each 


of  which  notches  a  different  volume  is  obtained  from  the  tank 
beneath. 

A  grinder  by  Messrs  Mayer  &  Schmidt,  of  Offenbach  a/Main, 
adapted  for  dry  or  wet  grinding,  is  illustrated  in  Fig.  271.  It  is 
fitted  with  an  exhaust  fan  to  remove  dust,  and  the  details  of  the 
arrangement  are  novel  and  interesting,  because  the  means  which 
are  provided  for  the  removal  of  the  dust  are  contained  in  the  ordi 
nary  framework  of  the  machine,  doing  away  with  the  necessity  of 
having  special  dust  collectors.  The  rests  themselves,  a,  a,  are  made 
hollow,  and  brought  into  communication  with  the  hollow  pedestal 
B,  which  is  completely  enclosed,  and  more  than  half  filled  with  a 
solid  filtering  material,  preferably  coke.  The  ventilating  exhaust 


TOOL  GRINDING  AND  SHARPENING. 


199 


fan  c  is  in  communication  with  the  hollow  space,  and  is  driven 
from  a  belt  on  the  collar  of  the  wheel  flange.  The  dust  is  there¬ 
fore  drawn  directly  from  the  spot  where  it  is  produced,  through 
the  hollow  rest  into  the  pedestal,  where  it  is  caught  by  the  coke 
and  falls  down  into  it,  the  large  area  of  the  space  being  favourable 
to  its  quiet  deposition.  The  deposit  can  be  cleaned  out  at  inter¬ 
vals.  It  is  pointed  out  as  one  of  the  minor  good  features  of  th,is 
arrangement  that  the  dust  of  brass  and  copper  can  be  recovered 
for  remelting.  For  wet  grinding,  a  centrifugal  pump  is  fitted. 

The  remarks  immediately  succeeding  relate  to  the  actual 
mechanical  work  of  grinding,  and  sharpening  wood-working 
tools. 

Nothing  can  compensate  for  the  absence  of  a  good  cutting 
edge  on  a  tool.  Mere  muscular  force  will  not  make  a  bad  instru¬ 
ment  cut  well,  files  and  glass-paper  are  of  little  use  where  accurate 
results  are  required,  and  quite  out  of  place  in  the  best  work  of  all. 
The  keenest,  finest  edges,  and  lines  should  be  left  as  the  tool 
makes  them.  Hence  frequent  recourse  to  the  grindstone  and 
hone  is  necessary,  and  not  less  essential  is  the  knowledge  how  to 
employ  these. 

The  grinding  of  a  cutting  tool  is  not  an  easy  task,  especially 
one  having  wide  edges,  such  as  those  of  broad  chisels,  and  plane 
irons.  As  the  angles  of  tool  edges  for  various  materials  are  con 
stant,  various  mechanical  contrivances  have  been  devised  for  hold¬ 
ing  them  at  set  angles  while  being  ground,  in  order  to  supplement 
the  efforts  of  unskilful  hands.  There  is  little  objection  to  these, 
but  they  may  be  regarded  in  the  same  light  as  a  swimmer  regards 
corks,  as  being  more  of  the  nature  of  an  encumbrance  than  other¬ 
wise.  By  long  practice  the  workman  learns  to  feel  the  bedding  of 
the  tool  upon  the  stone,  and  knows  at  once  when  the  facet  has 
moved  away  from  contact.  Moreover,  a  mechanical  aid  means, 
that  whether  the  stone  be  true  or  not,  the  tool  must  remain  stiffly 
in  one  position,  to  partake  of  its  misshapen  outline,  where  such 
exists,  while  by  unassisted  hand  grinding,  accurate  results  may  be 
obtained  even  from  a  badly  shaped  stone.  The  use  of  fixings  is 
therefore  generally  more  troublesome  than  grinding  by  hand  alone. 

In  grinding  a  plane  iron,  the  stone  should  revolve  towards  the 
iron,  not  away  from  it.  It  is  comparatively  easy  to  hold  the  iron 
firmly  while  the  stone  is  thrusting  it  towards  the  worker,  but  diffi¬ 
cult  to  hold  it  steadily  under  the  opposite  conditions.  The  top 


200 


TOOLS. 


iron  is  usually  screwed  in  its  place  on  the  cutting  iron,  but  a  little 
further  back.  It  serves  as  a  guide  to  grinding  square  across. 

When  grinding  firmer,  or  outside  gouges,  and  round-nosed 
tools,  the  curve  of  the  face  involves  a  frequent  change  of  position 
of  the  tool,  which  is,  in  the  former,  effected  by  a  rotary  motion  of 
the  wrist,  in  the  latter  by  a  horizontal  sweep  of  the  hand.  In 
grinding  the  gouge,  the  tool  is  held  parallel  with  the  edges  of  the 
stone,  and  rotated  on  its  longitudinal  axis,  and,  owing  to  its  hollow 
form,  the  angle  which  the  facet  forms  with  the  cutting  face  be¬ 
comes  constant  all  round.  But  in  grinding  the  round  nose,  the 
tool  must  be  rotated  round  the  point,  or  cutting  edge,  else  the 
angle  of  the  facet  would  not  be  constant. 

Paring  gouges  are  troublesome  to  grind,  unless  a  special  stone 
is  available.  In  many  shops  they  have  to  be  reduced  on  the  edges 
of  the  large  grindstone — easily  done  when  dealing  with  large  flat 


Fig.  272, 


Fig.  273, 


gouges,  but  unsuitable  with  the  smaller,  quicker  ones.  Very  often, 
a  small  piece  of  grindstone  is  rigged  up  in  the  lathe,  and  turned 
to  take  gouges  of  various  radii  (Fig.  272,  a).  Ora  conical  stone  may 
be  fitted  to  the  lathe  (Fig.  272,  b),  or  a  lead  lap,  turned  conical,  and 
charged  with  emery  powder,  is  used  for  the  paring  gouges,  and  irons 
of  hollow  planes.  Dry  emery  must,  however,  be  used  cautiously, 
to  avoid  risk  of  overheating  the  steel. 

For  woodworking,  as  also  for  the  finer  metal-turning,  the  tools 
must  be  sharpened  in  addition  to  being  ground.  This  is  done 
upon  an  oilstone,  or  hone,  lubricated  with  oil.  Fig.  273  shows 
the  stone  in  cross  section  in  its  stock,  with  the  best  method  of 
fitting  the  cover.  The  result  of  sharpening  is  this :  a  thin  film 
or  strip  of  the  metal  is  abraded,  and  turned  over  by  the  friction  of 
the  tool  on  the  stone,  until  a  new  keen  edge  of  metal  is  obtained. 
Hence  it  is  necessary  that  the  iron  should  be  rubbed  until  there  is 


TOOL  GRINDING  AND  SHARPENING.  201 


a  sensible  “wire  edge,”  as  it  is  termed,  or  until  a  burring  over  of 
the  metal  is  obtained,  t[uite  perceptible  to  the  finger  when  it  is 
brought  along  the  face  up  to  the  edge.  But  this  burr  is  all  rubbed 
off  the  back,  or  chamfered  facet  of  the  tool — never  off  the  face — 
the  latter  being  simply  passed  over  the  stone  for  the  purpose  of 
thrusting  the  burr  backwards,  and  so  assist  in  its  detachment. 
Hence  the  tilting  of  the  faces  of  plane  irons  and  chisels  is  not  only 
detrimental  to  their  efficacy,  but  unnecessary  for  purposes  of 
sharpening.  The  wire  edge, 
too,  is  seldom  entirely  re¬ 
moved  by  sharpening,  and 
its  complete  separation, 
when  desirable,  is  effected 
either  by  stropping  it  on  a 
leather  strop  (Fig.  274),  or 
by  drawing  the  cutting  edge 
once  or  twice  along  the 
edge  of  a  piece  of  hard 
wood.  The  strop  in  Fig. 

274  is  made  by  gluing 
sections  of  leather  belting  into  a  stock,  similar  to  that  of  a  hone. 

Grinding  should  be  economised  as  much  as  possible.  To 
grind  a  tool  very  thin,  and  then  to  commence  sharpening  at  an 
obtuse  angle,  wastes  the  Substance  of  the  steel,  as  also  does  con¬ 
tinuing  to  grind  after  a  perceptible  burr  is  produced,  or  grinding 
lop-sided,  and  then  having  to  reduce  the  opposite  side  in  order  to 
bring  the  tool  square. 

With  a  chisel  newly  ground,  the  angle  for  sharpening  should 
be  sensibly  equal  to  that  at  which  it  leaves  the  grindstone,  and 
the  longer  it  remains  at  about  that  angle  the  better. 

It  is  practically  impossible  to  sharpen  exactly  at  the  ground 
angle  (unless  hollow  ground  on  a  small  stone,  like  a  razor).  There 
must  be  a  very  slight  amount  of  elevation,  in  order  to  get  a  clean 
and  straight  facet. 

A  paring  gouge  must  be  sharpened  upon  a  slip  of  hone,  either 
mounted  in  a  block,  in  oilstone  fashion,  or  more  commonly  held 
in  the  hand,  while  rubbed  on  the  gouge,  the  latter  being  rested 
against  the  bench  edge. 

Outside  gouges  are  sharpened  on  the  oilstone,  being  rubbed  up 
and  down,  though  not  precisely  like  a  chisel.  The  gouge  is  held 


202 


TOOLS. 


sideways,  and  rotated  in' the  hand,  through  the  arc  formed  by  its 
cutting  edge,  being  moved  longitudinally  meanwhile.  The  slip 

then  removes  the  burr  from  the  hollow  face. 

Oil  slips  (Fig.  275)  are  in  such  constant 
request  for  gouges  of  both  kinds,  as  well  as 
Fig-  275.  for  hollow,  beading,  and  moulding  planes, 

and  spokeshaves,  that  several  are  necessary 
to  the  workman,  three  or  four  at  least.  One  slip  wall  do  duty  for 
four  sweeps,  its  two  edges  permitting  each  of  two  sweeps,  one  at 
each  end,  merging  at  the  centre.  Among  oilstones  and  slips  there 
are  none  better  (Turkey,  of  course,  excepted)  than  Charnley 
Forest,  as  they  are  called.  They  come  from  Charnwood  Forest, 


in  Leicestershire,  and  are  so  uniform  in  quality  that  a  stone  of 
that  kind  can  almost  always  be  depended  on. 

The  conditions  to  be  fulfilled  in  a  precision  grinding  machine 
for  common  tools  for  lathe,  planer,  slotter,  &c.,  must  include  those, 
which  govern  the  shapes  of  all  tools  used — straightforward,  bent, 
round-nosed,  and  prismatic,  with  varying  clearances  and  varying 
degrees  of  top  rake.  To  fulfil  these  entirely,  the  tool-holder  must 
be  capable  of  universality  of  movement,  easily  adjustable,  and 


TOOL  GRINDING  AND  SHARPENING.  203 


having  provision  for  precise  measurement  of  angles  ;  and  the  more 
nearly  a  grinding  holder  fulfils  these  conditions,  the  better  are  its 
claims  to  favourable  consideration.  Two  primary  circular  move¬ 
ments  must  be  embodied  :  that  for  plan  angles,  and  that  for  clear¬ 
ance  angles.  Besides  this,  a  traverse  motion  of  the  tool  which  is 
being  ground  against  the  wheel  is  essential,  in  order  to  present 
fresh  facets  constantly,  and  so  prevent  glazing.  Another  is  an 


oscillatory  movement  for  round-nosed  tools.  Then  another  is 
required  to  maintain  the  face  being  ground  in  contact  with  the 
wheel,  as  the  face  is  reduced. 

There  are  two  successful  American  grinding  machines  for 
common  tools — the  Sellers,  the  older ;  and  the  Gisholt,  more  recent. 
There  is  a  resemblance  between  the  two  in  regard  to  the  use  of 
circles  of  division  for  adjusting  the  tool  angles  to  be  ground,  but 
the  details  of  construction  are  entirely  different  in  each  case.  In 


204 


TOOLS. 


each  the  tool  is  clamped  upon  its  base,  precisely  as  it  would  be  in 
the  clamp  of  the  rest  or  of  the  tool  box,  and  in  each  its  angles  are 
all  ground  without  altering  its  position  in  the  holder. 

In  the  Sellers  machines  there  are  two  designs  embodied :  one, 
the  larger  size,  in  which  a  wheel  is  used  having  two  grinding  edges, 
of  vee  shape,  the  two  meeting  at  an  angle  of  90° ;  the  smaller 
machine  having  a  wheel  of  ordinary  plain  disc  shape.  The  large 
machine  deals  with  heavy  tools,  the  smaller  machine  takes  tools 
with  shanks  up  to  by  2  in. 


The  illustrations.  Figs.  276  to  285,  show  the  No.  i  tool  grind¬ 
ing  machine  of  Messrs  William  Sellers,  Inc.,  of  Philadelphia.  It 
is  a  universal  machine,  covering  all  the  tools  used  in  a  shop  on 
lathes,  planers,  shapers,  slotters,  &c.,  and  taking  tools,  the  shanks 
of  which  do  not  exceed  2|  by  2  in.  in  cross  section.  The  machine 
is  adapted  for  grinding  both  straight-faced  tools,  and  those  with 
curved  faces.  The  wheel,  of  vee  section,  is  convenient  for  grind¬ 
ing  different  surfaces,  and  for  producing  smoother  work.  The 
general  mechanism  is  as  follows : — 


TOOL  GRINDING  AND  SHARPENING.  205 


The  entire  machine  is  self-contained,  being  carried  on  the  tank- 
stand  A.  On  one  side  of  this  there  are  deep  angular  sliding  ways 
B,  which  carry  the  stem  c  of  the  main  tool  slide.  This  is  recipro¬ 
cated  vertically  by  the  handle  d,  and  as  the  mass  of  the  moving 
parts  is  counterbalanced  by  the  spiral  spring  e,  little  effort  is  re¬ 
quired  to  effect  the  movements.  The  tool  chuck  can  be  rotated 
in  a  horizontal  plane  about  the  vertical  axis  a,  Fig.  279,  parallel 
with  the  tool  shank,  and  set  by  the  graduated  arc  f,  and  a  vernier. 
It  can  also  be  rotated  about  the  horizontal  axis  bb,  bigs.  279  and 


280,  and  set  by  the  graduated  disc  g.  There  are  besides  two 
slides  H  and  j,  at  right  angles  with  each  other,  by  which  the  tool 
chuck  can  be  moved  parallel  to  the  tangent  planes  of  the  two 
grinding  surfaces  of  the  wheel.  There  are  two  chucks,  one  for 
grinding  straight-faced  tools,  the  other  for  those  having  curved 
faces,  by  means  of  a  former,  and  a  device  for  grinding  formers,  all 
of  which  are  shown  in  these  figures,  which  we  will  now  consider 
in  detail. 

The  case  of  straight-faced  tools,  or  those  the  cutting  edges  of 


206 


TOOLS. 


which  are  produced  by  the  intersection  of  plane  surfaces,  is  dealt 
with  by  the  sliding  movements,  and  circular  adjustments  just 


enumerated,  k,  Fig.  282,  is  the  chuck  used  for  these,  fitting  and 
revolvable  in  the  bearing  l. 


TOOL  GRINDING  AND  SHARPENING.  207 


The  case  of  curved-nosed  tools  involves  more  elaborate  me¬ 
chanism,  as  follows : — 

The  bearing,  l',  is  a  vibrating  one,  being  a  portion  of  a  swing- 


n 


Fig.  282. 


ing  frame  L  suspended  on  the  shaft  c,  Fig.  284,  in  the  supporting 
bearing  m,  which  of  course  partakes  of  the  motions  of  the  slides 
just  now  mentioned;  e  is  the  clamping  nut,  by  which  the  bearing 
M  and  its  swinging  frame  is  clamped  in  relation  to  the  quadrant 


F.  By  swinging  the  bearing,  the  axis  of  the  oscillating  chuck  is 
vibrated  toward  and  from  the  grinding  wheel. 

The  plain  chuck  K,  revolvable  in  the  bearing  l',  and  adjust¬ 
able  by  the  graduated  disc  g,  and  clamped  by  the  screw  aa, 


2o8 


TOOLS. 


encloses  a  sleeve  /,  which  is  a  journal  for  the  bearing  g  of  the 
oscillating  chuck,  the  upper  end  of  which  is  expanded  to  form  a 
head  //,  the  opposite  end  being  retained  by  a  screwed  collar  /,  by 
which  endlong  motion  is  prevented.  The  sleeve  is  clamped  by 
the  two  set  screws  /,  /,  seen  in  Figs.  279  and  282. 

The  tool-holding  mechanism  is  clamped  indirectly  to  the  head 
h  by  an  intermediate  slide  rest  N,  provided  with  a  traverse  pin  k, 
and  with  a  graduated  edge  at  /.  N  receives  the  tool  chuck  o,  in 
which  a  tool  is  seen  clamped  by  the  screws  m.  This  slide  rest  is 
capable  of  traverse  movement  along  the  pin  k.,  by  means  of  the 
central  locking  bolt  n,  as  follows : — 

The  bolt  n  has  a  head  at  one  end  fitting  in  a  recess  in  the  slide 


rest,  and  at  the  other,  is  fur¬ 
nished  with  a  hinged  handle  P, 
with  cam -shaped  cheeks,  which 
either  press  against  the  end  of  the 
journal  or  are  released  there¬ 
from,  by  moving  the  handle  p  up 
or  down  on  its  pivot,  so  locking, 
or  releasing  the  rest  N  on  the 
head  h.  Or,  on  release,  the  bolt 
n  can  be  turned  on  its  axis,  by 
which  movement  teeth  cut  on  its 
head  engage  with  teeth  in  the 
rest,  and  so  slide  the  latter  in  one 
direction  or  the  other  along  the 
pin  k.  The  tool  jaw  o  is  pivoted 
in  the  hole  <?,  and  clamped  in  the 


Fig.  284. 


curved  slot  /  by  the  bolt  q.  A  pin  r  locks  the  jaw  o  in  a  hori¬ 
zontal  position,  when  placing,  or  removing  the  tool.  But  when 
grinding  is  being  done,  the  pin  is  drawn  back,  allowing  the  jaw  to 
oscillate  freely  about  its  axis  in  the  vibrating  bearing  L,  through  about 
180°,  for  presenting  the  contour  of  the  round-nosed  tool  to  the 
grinding  wheel.  And  this  brings  us  to  the  action  of  the  former 
plate  shown  at  s,  Fig.  283,  and  which  fits  into  the  recess  /  of  the 
head  h  of  the  journal  g  in  Fig.  282,  being  checked  therein  with  a 
rectangular  notch,  s  is  in  contact  with  a  roller  /,  carried  on  a  stud  in 
a  stand /',  Fig.  283,  fitting  by  two  bolts  into  the  main  bearing  m,  one 
of  the  bolt  holes  being  seen  at  u,  Fig.  282,  and  both  in  Fig.  281. 

The  counterweighted  lever  q  is  employed  to  press  the  former 


TOOL  GRINDING  AND  SHARPENING.  209 


plate  s  against  the  roller  /,  and  it  holds  the  plate  against  the  roller 
with  sufficient  force  to  ensure  the  vibrating  motion  of  the  chuck. 
The  tool,  pinched  in  the  jaw  o,  is  rotated  about  the  former  plate  s, 
by  the  handle  r,  and  its  shape  will  depend,  subject  to  the  shape  of 
the  plate,  on  the  relation  which  its  position  inwards  or  outwards, 
bears  to  that  of  the  former  i’,  and  will  range  from  an  exact  counter¬ 
part  of  the  former,  but  on  a  reduced  scale,  to  a  pointed  round¬ 
nosed  tool. 

An  indicator  u  is  provided  to  determine  the  distance  to  which 
a  tool  s  should  project  beyond  the  axis  of  the  oscillating  chuck 
when  clamped  in  its  jaw.  Its  curve  corresponds  with  that  of  the 
average  curvature  of  the  grinding  wheel.  It  is  attached  by  an  arm 
to  the  shaft  v,  which  turns  and  slides  freely  in  the  bearings  w. 


Fig.  285, 


A  weighted  lever  a:  presses  against  the  boss  of  u\  and  its  finger 
indicates  divisions  on  the  arc  jy,  and  thus,  the  distance  out  at  which 
the  tool  makes  contact  with  the  indicator.  In  this  way  a  tool  can 
be  set,  leaving  the  slight  allowance  for  grinding  off,  or  when  a  tool 
has  been  ground,  the  number  can  be  read  off,  and  used  as  a  guide 
for  grinding  similar  tools  at  any  other  time. 

The  wheel  head  is  shown  in  section  in  Fig.  285.  It  is  adjust¬ 
able  bodily  on  tee  slots  in  a  plate  cast  with  the  tank-base  of  the 
machine.  A  centrifugal  pump  is  enclosed  in  the  tank,  driven  by 
the  pulleys  t.  The  pillar  u  carries  a  light  crane  used  for  changing 
wheels  on  the  spindle, 

Messrs  Sellers  have  prepared  charts,  giving  the  most  approved 
angles  and  clearances  for  various  cutting  tools,  together  with  par¬ 
ticulars  of  what  formers  should  be  used,  and  position  of  index 


210 


TOOLS. 


finger  to  be  set.  A  drawing  (Fig.  286)  shows  typical  round-nosed 
tools,  both  straightforward,  and  bent,  with  the  angles  marked. 

In  the  Gisholt  grinder 
there  are  the  two  move¬ 
ments  of  rotation  :  that  in 
the  horizontal,  and  that  in 
the  vertical  plane  about  the 
axis  of  the  tool.  The  frame 
which  carries  the  circles  and 
the  tool-holder,  shown  in 
Fig.  287,  is  carried  in  the 
pan  of  the  machine,  the 
whole  being  capable  of 
oscillation  in  a  vertical 
plane,  in  order  to  permit 
of  the  traverse  of  the  tool  against  the  emery  wheel  during  grinding. 
The  oscillation  is  effected  through  a  large  arm  of  circular  section, 
which  is  fitted  into  a  boss  in  the  supporting  column,  the  emery 
wheel  having  its  arbor  in  the 
top  of  the  column,  and  it  is 
easily  effected  by  the  workman 
through  a  lever  attached  to  the 
pan.  To  move  the  tool  forward, 
as  grinding  reduces  its  face,  the 
pan,  with  the  tool-holder,  &c., 
is  traversed  by  a  hand  wheel 
and  screw,  operated  by  the  left 
hand  of  the  attendant,  while 
the  right  hand  is  engaged  in 
manipulating  the  lever.  The 
emery  wheel  used  is  hollow,  and 
conical  in  section  (Fig.  288). 

Its  front  face  is  used  for  grind¬ 
ing,  it  is  protected  by  a  hood ; 
and  a  water  pipe,  grinding 
chart,  &c.,  are  attached.  The 
holder  (Fig.  287)  permits  of 
the  following  adjustments  for  angle :  In  the  horizontal  plane  it 
can  be  rotated  through  about  320°,  which  gives  plan  angles  of 
tools,  including  those  which  are  bent  to  right  or  left  hand ;  in  the 


TOOL  GRINDING  AND  SHARPENING. 


21  I 


vertical  plane  the  tool  can  be  rotated  through  a  complete  circle 
round  the  tool  axis,  which  allows  of  grinding  the  top,  and  both  sides. 
There  is  also  provision  for  a  movement  of  the  tool  to  30°  on  each 
side  of  the  centre  line  of  the  holder,  to  bring  the  faces  of  bent  tools 
parallel  with  the  face  of  the  emery  wheel ;  and  another  of  15°  on 
each  side  of  the  horizontal, 
specially  for  grinding  the 
clearances  on  threading  tools. 

The  problems  of  mechani¬ 
cally  grinding  single-edged 
tools  are  of  a  different  char¬ 
acter  from  those  which  arise 
when  the  multiple-edged  tools 
have  to  be  ground  and  sharp¬ 
ened.  The  latter  have  given 
rise  to  some  scores  of  different 
kinds  of  machines  of  universal  character,  that  is,  capable  of  grind¬ 
ing  all  the  shapes  of  milling  cutters,  reamers,  taps,  drills,  &c. 
We  cannot  give  details  of  these,  but  must  simply  illustrate  one 
machine  of  this  kind,  and  give  a  few  examples  of  how  the  work 
is  done. 


Fig.  289. 


The  work  which  a  machine  must  be  capable  of  performing 
includes  the  following  operations  : — Grinding  the  teeth  on  plain 
parallel  cutters,  with  the  grinding  wheel  axis  parallel  with  the  cutter 
axis,  Fig.  289,  a,  a  tooth  rest  being  used  to  keep  each  tooth  at  the 
correct  height  as  it  is  brought  round  for  operating  on.  Grinding 
the  sides  of  cutters,  when  teeth  are  formed  upon  them,  as  at  b. 
Deepening  the  flutes,  or  cutting  them  from  the  solid,  may  be  done 


212 


TOOLS. 


as  at  c,  using  a  wheel  having  its  edge  formed  to  suit  the  job.  This 
is  an  alternative  to  milling.  Taps  are  sharpened  as  at  d,  using  a 
cup  wheel  to  grind  the  cutting  face.  A  similar  class  of  work  is 
shown  at  E,  but  on  backed-off,  or  relieved  cutters,  which  are  thus 
sharpened  without  changing  their  form.  Reamers  are  most  con¬ 
veniently  sharpened  as  at  f,  where  a  cup  wheel  travels  along  the 
edge,  and  leaves  a  flat  surface,  the  suitable  amount  of  clearance 
being  obtained  by  tilting  the  reamer  down  as  shown.  Tapered,  or 
bevelled  cutters  are  ground  by  angling  the  table  of  the  machine,  or 
the  wheel  head,  to  suit  the  required  bevel,  as  at  g.  An  extreme 
case  of  angling  is  shown  at  h,  being  a  rose  reamer,  or  broach, 
having  its  end  teeth  being  touched  up.  Profile  grinding  occupies  a 
large  place,  and  many  machines  are  fitted  with  attachments  for 
shaping  cutters  with  irregular  edges,  for  milling  special  forms  of 
work.  The  principle  in  all  these,  however,  is  that  shown  at  j,  either 

the  wheel  head,  or  the  cutter 
slide  being  controlled  by  the 
motion  of  the  tracer  wheel  seen, 
which  is  held  against  the  former 
plate,  of  appropriate  profile,  and 
so  produces  the  identical  profile 
on  the  cutter.  Some  types  of 
machines  have  a  pantagraph 
device,  for  profiling  cutters  either 
larger  or  smaller  than  the  former.  The  grinding  of  spiral 
toothed  cutters  presents  no  special  difficulty,  many  of  the  above- 
mentioned  cutters  being  made  of  this  kind,  as  well  as  straight 
toothed.  Either  an  ordinary  tooth  rest  is  employed,  against 
which  the  cutter  teeth  are  slid,  or  a  spiral  head  is  fitted  to 
the  machine,  giving  the  desired  twist  to  the  cutter  as  it  is  being 
ground.  Knife,  and  shear  blades  are  ground  by  simply  presenting 
their  edges  at  a  suitable  angle  to  a  cup  wheel  as  shown  at  k. 
These  examples  do  not  exhaust  the  different  methods  of  grinding 
cutters,  but  they  are  representative,  and  most  other  ways  are  modi¬ 
fications  of  them.  In  addition  to  tooth  grinding  proper,  machines 
are  adapted  to  certain  preparatory  work,  which  must  be  done,  as 
grinding  out  the  holes  true  in  the  cutters,  so  that  they  shall  fit  their 
mandrels  accurately,  also  facing  the  sides  of  cutters  and  washers, 
ensuring  true  bearing  faces.  The  arbors  or  mandrels  are  also  trued 
up  between  centres,  so  that  a  tool-grinding  machine  is  really  a 


A  B  C  D  E  F  G 


Fig.  290. 


TOOL  GRINDING  AND  SHARPENING.  213 

cylindrical  grinder  as  well,  a  pulley  being  provided  for  driving  the 
work. 

The  most  generally  useful  forms  of  wheels  are  shown  in  Fig. 
290,  the  first  four  types,  a,  b,  c,  and  d,  being  cup  wheels,  and 
used  more  often  than  any  other  forms,  a  and  b  are  wheels  of 
heavier  type  than  c  and  d,  the  latter  being  employed  for  the  most 
delicate  work,  for  which  a  and  b  are  not  so  well  adapted,  e,  f, 


Fig.  291. 


and  G  are  thin  wheels,  used  for  sharpening  of  various  kinds,  includ¬ 
ing  saw  teeth.  Wheels  like  g,  but  wider,  are  employed  extensively 
for  cylindrical  grinding  of  arbors,  and  similar  plain  work.  It  is 
impossible  to  say,  however,  that  any  one  wheel  is  suitable  for  one 
class  of  work  only,  because  all  are  used  in  turn  by  different  grinders, 
according  to  the  ideas  of  the  workmen. 

Fig.  291  shows  a  universal  machine  by  Messrs  Alfred  Herbert, 


214 


TOOLS. 


Ltd.,  of  Coventry,  which  embodies  all  the  essential  features  of  a 
good  grinder.  It  is  suitable  for  heavy  as  well  as  light  grinding. 
The  basis  of  the  framing  is  a  circular  column,  round  which  the 
tables  can  be  slewed  to  present  the  work  to  the  wheels  in  any 
desired  attitude.  The  tables  are  raised  or  lowered  by  hand  wheel, 
bevel  wheels  and  screw,  and  they  are  fed  in  one  of  two  ways,  either 
quick  or  slow,  for  coarse  and  fine  adjustments;  for  the  first,  the  hand- 
wheels  are  turned,  and  actuate  a  pinion  and  rack  direct,  for  the 
second,  a  worm  is  thrown  into  engagement  with  a  wheel  on  the 
pinion  shaft  and  driven  by  a  small  hand  wheel,  seen  in  the  photo, 
thus  producing  a  delicate  and  slow  motion  for  grinding.  The  top 
table  swivels  for  grinding  angular  work,  and  is  clamped  where 
desired.  Several  classes  of  work  may  be  done  with  the  headstocks 
provided  on  the  table,  from  grinding  between  dead  centres,  to 
overhanging  arbor  work,  and  circular  grinding ;  a  dividing  attach¬ 
ment  is  included  for  grinding  flutes,  machine  relieved  cutters,  &c. 
A  universal  swivel  vice  may  also  be  held  on  one  of  the  heads,  for 
presenting  pieces  of  irregular  form,  or  pieces  at  any  angles  desired. 
The  wheel  head  carries  two  wheels,  one  at  each  end  of  the  spindle, 
for  various  classes  of  jobs,  and  a  distinct  high-speed  attachment  is 
located  at  one  side,  carrying  small  wheels  for  internal  grinding, 
and  driven  by  friction  wheel  from  the  main  spindle.  A  feature  of 
the  machine  is  that  a  liberal  supply  of  water  can  be  flooded  on  to 
the  cutters,  enabling  them  to  be  kept  cool  under  heavy  cuts.  A 
centrifugal  pump  at  the  base  of  the  machine  forces  the  water  up 
through  the  flexible  pipe,  direct  on  to  the  wheel,  covered  with  a 
guard,  and  trays  are  provided  which  catch,  and  direct  the  water 
downwards  to  the  tank  again,  where  it  is  strained,  and  pumped  up 
again. 


SECTION  VI. 

TOOLS  FOR  MEASUREMENT  AND  TEST. 


CHAPTER  XIX. 


Standards  of  Measurement. 


Definition— Rule  and  Gauge  Measurement— Standards— Temperature — Inter¬ 
changeability — Limits  of  Accuracy — Early  English  Standards  of  Measure¬ 
ment — Basis  of — Pratt  &  Whitney  Standards — Details — Line  Measures, 
and  End  Measures— Refined  Tests— Rules— Varied  Forms  of— Use  and 
Wear — Scales — Forms  of — Tapes — Rods. 

CORRECT  definition  of  measurement  would  be,  the 


testing  of  the  dimensions  of  a  piece  of  work  with  reference 


to  a  standard  agreed  upon.  This  would  exclude  the  em¬ 
ployment  of  straight-edges,  squares,  bevels,  or  calipers  which  are 
used  to  test  mathematical  relations.  Yet  these  should  certainly  be 
included  in  any  complete  account  of  the  methods  of  measurement. 

The  testing  of  dimensions  is  elfected  with  reference  to  the 
standard  of  the  rule  or  the  gauge.  Though  the  latter  is  derived 
from  the  former,  the  present  tendency  is  towards  the  increasing 
use  of  the  last  named,  at  the  expense  of  the  first.  The  rule  is 
seen  and  used  less,  and  the  gauges  more.  But  each  has  its  own 
definite  place  in  the  economy  of  the  workshop.  The  common  use  of 
the  rule  is  lessened  also  by  the  employment  of  templets  and  jigs  ; 
but  these  also  have,  like  the  gauges,  to  be  derived  from  that  instru¬ 
ment,  dimensions  being  transferred  by  direct  measurement,  or  more 
often  by  the  points  of  compasses,  dividers,  or  trammels. 

The  great  difference  between  rule  measurement,  or  that  taken, 
and  transferred  therefrom  by  the  points  of  compasses,  &c.,  and  of 
gauge  measurement,  is  that  the  sense  of  vision  is  relied  on  in  the 
first,  and  the  sense  of  touch  in  the  second.  This  is  a  most  impor- 


2i6 


TOOLS. 


tant  distinction,  because  the  sense  which  feels  the  contact  of  parts 
is  capable  of  detecting  more  minute  differences  than  the  eye,  unless 
the  latter  be  assisted  by  magnifying  glasses.  And  magnification  is 
not  of  much  use  unless  assisted  by  the  mechanical  control  of  an 
instrument. 

Take  a  steel  rule  used  by  workmen  :  the  finest  dimensions 
are  seen  to  be  one-hundredths  of  an  inch,  into  which  perhaps  one 
particular  inch  only  is  divided.  Now  one-hundredth  of  an  inch, 
though  very  fine  as  a  visible  subdivision  on  the  rule,  is  one  that  is 
seldom  worked  by  when  compass  measurement  is  resorted  to.  It  is 
but  the  thickness  of  a  compass  line,  to  one  side  or  other  of  which 
a  man  may  work  in  machine  tool  or  vice,  and  be  considered  a  neat 
workman  in  doing  so.  Actually  the  sixty-fourth  of  an  inch  is  the 
finest  rule  dimension  of  which  any  account  is  usually  taken  in  the 
shops,  though  it  is  often  qualified  as  being  “  full  ”  or  “  bare.”  Yet 
one-hundredth  of  an  inch  is  extremely  coarse  in  any  system  of 
gauging,  for  which  in  ordinary  work  it  would  have  to  be  divided  by 
ten  or  twenty. 

'I'he  proper  places  of  these  two  systems  of  rule  and  compass, 
and  of  gauging  instruments  may  now  be  settled.  The  time  is 
rapidly  vanishing  when  the  turner  and  machinist  will  check  their 
work  by  direct  reference  to  the  rule.  But  the  liner-out  must  still 
employ  the  rule  and  compass,  or  the  equivalent  templet,  which 
depends  for  its  accuracy  on  rule  and  compass.  As  the  work  of  a 
shop  becomes  more  highly  specialised,  the  direct  rule-and-compass 
methods  give  place  to  the  use  of  templets  for  lining-out,  and  of 
jigs  for  machining. 

There  are  two  kinds  of  rule  measurement,  and  two  of  gauge 
measurement.  The  rule  may  be  used  directly,  or  the  compasses  can 
be  used  for  transference  therefrom.  The  gauge  may  be  movable, 
or  fixed,  and  each  method  makes  a  great  difference  in  results,  and 
corresponds  with  diverse  shop  systems. 

Into  the  modern  system  of  measurement  many  matters  enter. 
In  the  first  place  we  must  take  the  broad  fact  that  engineering 
work  is  international  in  character,  and  that  this  involves  a  uniform 
standard  of  reference  for  dimension  units.  The  demands  are 
such  that  a  shaft  made,  say,  in  England,  will  fit  a  hole  bored  in 
America  ;  that  taps  and  dies  made  in  any  country  to  a  given  stand¬ 
ard  will  be  exactly  alike ;  that  gauges  will  be  depended  on  within 
certain  limits,  irrespective  of  distance  or  time.  Here,  then,  the 


STANDARDS  OF  MEASUREMENT 


217 


question  of  standards  conies  in,  which  is  a  most  difficult  one,  to 
the  solution  of  which  the  abilities  of  the  best  mathematicians  and 
mechanicians  have  been  brought  to  bear. 

Having  the  question  of  standards  settled,  the  problem  of  tem¬ 
perature  has  to  be  grappled  with.  Since  materials  change  their 
dimensions  with  every  change  in  temperature,  however  minute,  and 
as  shops  range  anywhere  between  40°  and  90°  F.,  a  definite  tem¬ 
perature  has  to  be  settled  on,  at  which  alone  measuring  instruments 
shall  be  standard.  Metal  also  undergoes  slow  changes  which, 
though  negligible,  like  temperatures,  in  coarse  dimensions,  have  to 
be  counted  on  in  the  very  finest  measurements.  The  mechanical 
difficulties  of  manufacture  increase  with  refinements  in  measure¬ 
ment,  making  the  production  of  standards  a  task  requiring  infinite 
patience  and  the  highest  possible  technical  skill  and  care.  Then, 
after  these  are  obtained,  the  work  of  transferring  and  reproducing 
dimensions  on  various  gauges  and  measuring  tools  is  one  that  is 
fraught  with  difficulty,  so  that  the  production  of  the  finest  measur¬ 
ing  instruments  and  tools  remains  the  speciality  of  a  few  firms. 

The  greatest  impetus  to  the  use  of  high-class  instruments  of 
measurement  has  been  due  to  the  growth  of  the  interchangeable 
system,  for  a  concise  explanation  of  which,  see  page  3. 

To  secure  such  results  without  an  enormous  cost  for  labour, 
the  work  of  the  machines,  and  the  measuring  instruments  must  be 
exact,  and  correlated.  The  tools  must  be  capable  of  producing 
parts  so  accurately  that  only  by  chance  or  accident  will  any  devia¬ 
tions  occur  from  uniformity  in  the  pieces  made.  The  measuring 
instruments  also  must  be  capable  of  ready  application.  And  be¬ 
hind  all  these  is  the  paramount  problem  of  cost,  for  economy  is  an 
essential  dominating  factor  in  production.  The  fallible  human 
element  must  be  nearly  eliminated,  and  the  skilled  mechanic  give 
place  to  the  machine  minder,  and  the  gauger,  who  may  be  a  mere 
boy  or  girl. 

In  speaking  of  accuracy,  it  is  as  well  to  observe  that  no  one 
understands  this  to  mean  absolute  truth,  which  is  impossible  of 
attainment.  The  term  is  relative  only,  and  its  degree,  or  the 
measure  of  approximation  to  truth  is  different  in  different  classes 
of  work,  and  to  these  varying  degrees  some  measuring  instruments 
are  adapted.  In  some  classes  of  rough  work  one-hundredth  of  an 
inch  is  a  sufficiently  fine  approximation ;  in  others  one-thousandth 
is  too  coarse.  Now  one  excellent  feature  of  the  modern  system  is 


2i8 


TOOLS. 


that  the  degree  of  accuracy  permissible  in  any  given  class  of  pro¬ 
duct  is  predetermined,  and  embodied  in  the  setting-up  of  machines, 
and  in  the  measuring  instruments  used,  so  that  when  once  fixed 
up  by  a  trained  mechanic  or  toolmaker,  no  further  skill  is  required 
for  the  operation  of  the  first,  or  the  application  of  the  second. 
Since,  also,  no  machine,  however  carefully  fixed  up,  can  be  depended 
on  to  produce  a  large  number  of  similar  parts  precisely  alike,  the 
variation  from  exact  accuracy  which  is  permissible  is  also  pre¬ 
determined,  and  embodied  in  the  measuring  instruments  used,  so 
that  a  boy  or  girl  when  gauging  by  the  sense  of  touch  can  tell  in 
an  instant  whether  a  piece  is  above  or  below  the  limits  which  are 
permissible. 

It  is  clear  that  this  system  of  interchangeability  is  not  suited 
for  all  classes  of  work,  but  that  to  be  economical  and  successful 
a  very  large  number  of  similar  pieces  must  be  required.  This 
would  appear  to  lessen  its  value,  and  to  bar  its  use  in  many  shops 
that  chiefly  handle  general  work.  So  it  does,  but  not  to  the 
extent  which  may  be  supposed.  The  introduction  of  a  good 
system  is  better  than  working  without  system,  in  a  heterogeneous 
fashion.  There  are  few  shops  in  which  the  work  is  of  so  very 
general  a  character  that  there  are  no  parts  of  mechanisms  which 
do  not  recur  in  large  numbers.  The  commonest  are  small  screws, 
bolts,  studs,  and  pins — just  the  work  for  special  machines  and 
methods  of  measurement.  But  when  once  a  system  is  introduced, 
it  tends  to  extension,  and  to  applications  not  anticipated,  and 
therefore  when  a  firm  can  see  its  way  to  make  a  good  system 
fairly  pay  its  way,  it  is  best  to  take  it  up. 

The  earliest  measurements  were  derived  from  well-known 
objects.  Every  one  remembers  “Three  barleycorns  make  i  inch  ; 
12  inches,  i  foot;  3  feet,  i  yard.”  By  Statute  17  Edward  II., 
1324,  it  was  enacted  that  “Three  barleycorns,  round  and  dry, 
make  i  inch;  and  12  inches,  i  foot.”  Thirty-six  barleycorns 
would  therefore  make  i  foot,  but  they  would  not  be  so  reliable  as 
twelve  bronze  halfpence  placed  edge  to  edge,  which  give  that 
measurement  very  exactly.  That  standard,  if  it  may  be  so  termed, 
remained  lawful  for  five  hundred  years,  until  in  1824,  by  the  Act 
5  (leorge  IV.,  cap.  74,  it  was  declared  that  a  yard  bar  made  by 
Bird  in  1760  was  “declared  to  be  the  extension  called  a  yard; 
and  that  the  same  straight  line  or  distance  between  the  centres 
of  the  said  two  points  in  the  said  gold  studs  in  the  said  brass  rod. 


STANDARDS  OF  MEASUREMENT 


219 


the  brass  being  at  the  temperature  of  62°  by  Fahr.  thermometer, 
shall  be  and  is  thereby  denominated  the  ‘  Imperial  standard  yard.’  ” 

It  must  not  be  supposed  that  the  legalisation  of  the  standard 
coincided  with  an  awakening  to  the  necessities  of  a  better  system. 
In  this,  as  in  other  matters,  the  Legislature  but  followed  the 
leading  of  the  Time  spirit.  In  1791  the  French  Commission 
adopted  the  length  of  a  ten-millionth  part  of  the  quadrant  of 
the  earth’s  meridian  as  a  metric  basis.  Curiously,  too,  this 
coincided  almost  exactly  with  the  length  of  a  seconds  pendulum, 
researches  into  the  beating  of  which  had  long  engaged  the  close 
attention  of  physicists,  since  the  time  when  it  was  proposed  by 
Huyghens  in  1670,  and  Picard  in  1671,  as  a  basis  of  measurement. 
The  length  of  the  seconds  pendulum,  39  in.,  is  not  so  constant  as 
to  be  a  reliable  standard  of  reference,  because  of  the  influence  of 
minute  errors  due  to  the  temperature,  latitude,  and  weight  of  air. 
Later  proposals  have  been  to  utilise  as  a  basis  some  unalterable 
minute  measurement  such  as  the  length  of  a  wave  of  sodium  light. 

But  proposals  of  this  kind  will  not  now  find  favour,  because 
the  original  bases,  though  demonstrated  since  to  have  been 
inaccurate,  are  now  crystallised  in  standard  bars  carefully  pre¬ 
served  in  all  civilised  countries  for  the  purpose  of  reference.  The 
history  of  these  bars  is  a  tribute  to  the  patient  and  loving  labour 
of  many  men,  to  whom  the  whole  world  owes  much,  yet  whose 
names  are  little  known  outside  the  world  of  scientists  and  scien¬ 
tific  engineers.  All  the  measuring  instruments  used  to-day  are 
referable  to  some  original  standards,  not  directly,  but  through 
intermediate  or  secondary  standards  derived  from  them.  The 
original  standards  are  only  accurate  at  a  certain  temperature  at 
which  they  are  maintained.  They  are  mostly  in  charge  of  public 
bodies,  though  some  few  of  the  leading  manufacturing  firms  have 
exact  copies.  Nothing  is  ever  allowed  to  touch  the  originals  for 
the  purpose  of  transferring  dimensions.  But  microscopes  and  light 
reflections  of  a  most  elaborate  character  are  the  means  by  which 
transferences  are  effected. 

The  existing  English  standards  are  the  result  of  the  labours 
of  Sir  Francis  Baily  and  the  Rev.  R.  Sheepshanks.  The  original 
bar  referred  to  just  now  as  having  been  legalised  by  Act  5  George 
IV.,  and  which  had  been  constructed  by  Bird  in  1760,  was 
destroyed  by  the  fire  which  consumed  both  Houses  of  Parliament 
in  1834.  When  an  attempt  was  made  to  restore  it  by  reference 


220 


TOOLS. 


to  the  seconds  pendulum — a  contingency  which  had  been  pro¬ 
vided  against  by  the  Act  of  1824 — it  was  found  to  be  impossible, 
in  consequence  of  the  errors  inseparable  from  the  method. 
Consequently  the  new  yard  was  restored  laboriously  with  reference 
to  various  standards — five  in  number — in  existence,  none  of  which 
was  precisely  alike.  The  result  is  Bronze  No.  i,  which  is  kept 
in  the  Houses  of  Parliament.  It  is  composed  of  copper  16  parts, 
tin  2^,  and  zinc  i,  measures  38  in.  long,  i  in.  wide,  and  i  in.  deep, 
and  the  graduations  are  marked  on  gold  plugs  sunk  into  the 
bar  36  in.  apart,  the  top  faces  of  the  plugs  being  half  way  down 
the  thickness  of  the  bar.  The  reason  of  locating  them  so  was  to 
neutralise  the  difference  in  length  which  would  be  caused  by 
flexure  of  the  bar.  About  forty-four  copies  were  made,  which  are 
in  the  possession  of  various  public  institutions  at  home,  and  of 
foreign  Governments.  They  were  legalised  by  Act  of  Parliament, 
30th  June  1855.  All  these  are  made  of  the  same  class  of  bronze, 
termed  “  Baily’s  metal,”  so  that  they  would  all  expand  at  similar 
rates,  and  corrections  for  temperature  could  be  made  alike  in  all. 
The  temperature  at  which  the  standard  yard  is  measured  is  62°  F. 
There  is  therefore  no  such  thing  as  a  standard  inch.  The 
standard  is  the  yard,  which  has  to  be  subdivided  by  manufacturers. 
The  standard  French  metre  is  termed  the  metre  of  the  Archives. 
It  is  made  of  platinum,  and  is  standard  at  0°  C.,  or  32°  F. 

The  man  who  handles  a  foot  rule  knows  little  of  the  labours 
which  have  been  accomplished  ere  he  could  obtain  that  rule. 
Before  its  manufacture  was  possible,  the  highest  labours  of 
physicists,  mathematicians,  and  scientific  mechanics  had  been 
brought  to  bear  for  more  than  a  hundred  years  past  on  the 
problems  of  measurement,  and  on  those  involved  in  the  materials 
used.  Differences  of  temperature,  differences  in  the  coefficients 
of  expansion  of  materials,  differences  in  density,  hardness,  or 
degrees  of  annealing,  differences  due  to  flexure,  errors  in  observa¬ 
tion,  the  fallible  human  element  in  making  and  measuring,  and 
much  else — all  these  problems  had  to  be  attacked,  and  the 
errors  ever  insuperable  therefrom  reduced  to  the  last  minimum. 

The  Pratt  &  Whitney  Company,  of  Hartford,  Conn.,  derived 
all  their  measurements  first  hand  from  the  imperial  standards,  for 
the  reproduction  of  which  they  engaged  the  services  of  Professor 
Wm.  A.  Rogers.  As  the  imperial  yard  of  Great  Britain,  No.  i  of 
Baily’s  metal,  could  not  be  available  for  ready  reference  by  an 


STANDARDS  OF  MEASUREMENT. 


221 


American  firm,  the  “Bronze  II.”  of  the  United  States  was 
selected.  This  was  presented  to  the  United  States  in  1856,  and 
was  stated  to  be  standard  at  61.79°  F.  By  reference  to  this, 
several  Pratt  &  Whitney  standards  were  prepared  for  end 
measure,  and  line  measure,  the  details  of  the  preparation  of 
which  are  much  too  lengthy  for  publication  here.  They  include 
bars  of  bronze,  of  tempered  steel,  and  of  annealed  steel.  The 
lines  are  also  variously  marked.  In  one  of  the  bronze  bars  41  in. 
long,  I  in.  wide,  and  i  in.  deep,  the  lines  are  marked  on  polished 
gold  plugs  inserted  in  the  bottom  of  wells  sunk  in  the  bar  to  the 
depth  of  half  an  inch,  at  intervals  of  12  in.  In  another  bronze 
bar  of  the  same  length,  platinum-iridium  plugs,  ^3^  in.  in  diameter, 
are  inserted  flush  with  the  surface  at  various  distances,  while  in 
one  of  the  tempered  steel  bars  40  in.  long,  in.  deep,  and  |  in. 
wide,  the  surface  is  polished  for  receiving  the  graduations.  An 
annealed  steel  bar  of  nearly  the  same  dimensions  has  tempered 
steel  plugs  inserted.  These  bars  were  prepared  by  the  Pratt  & 
Whitney  Company  at  their  own  shops,  and  the  depth  was  found 
to  be  so  nearly  parallel  that  the  surfaces  remained  in  focus  under 
the  microscope  of  the  comparator,  when  the  microscope  was 
moved  along  the  whole  length.  Microscopists  will  understand 
the  severity  of  this  test. 

The  flexure  of  such  bars,  even  though  slight,  would  of  course 
alter  the  lengths  marked  upon  them,  and  it  is  found  that  two 
points  of  support  ensure  better  results  than  attempting  to  support 
the  bars  along  their  whole  length.  It  is  found  that  if  the  points 
of  support  are  placed  at  the  ends  of  a  bar  41  in.  long,  the  change 
of  length  due  to  flexure  is  over  one-thousandth  of  an  inch,  which 
is  a  very  coarse  degree  of  error.  This  is  the  reason  why  in  some 
standards  the  defining  lines  are  traced  on  gold  plugs  sunk  to  the 
level  of  the  neutral  plane  of  the  bar,  where  the  effect  of  flexure 
is  eliminated.  But  then  difficulty  arises  in  reading  subdivisions. 
To  prevent  flexure,  points  of  support  must  be  placed  at  a  distance 
from  the  centre  equal  to  half  the  length  of  the  bar,  divided  by 
the  square  root  of  3.  If  the  supports  are  placed  nearer  the  centre, 
the  upper  surface  becomes  convex ;  if  nearer  the  ends,  the  upper 
surface  becomes  concave. 

Temperature  affects  the  standards  so  greatly  that  extreme 
precautions  were  necessary  when  transferring  or  comparing 
dimensions.  The  temperature  in  these  bars  was  kept  as  near 


222 


TOOLS. 


62°  F.  as  possible,  and  lines  were  drawn  in  some  cases  a 
thousandth  of  an  inch  apart,  the  middle  line  of  a  group  forming 
the  actual  defining  line.  In  this  connection  the  coefficients  of 
expansion  of  the  various  mixtures  used  came  in  for  study.  In 
order  to  ascertain  these,  lengthy  periods  of  observation  were 
found  to  be  necessary,  during  which  changes  in  length  under  a 
varying  temperature  had  time  to  become  permanent.  Thus,  mass 
and  conductivity  both  affected  the  result,  retarding  or  accelerating 
change.  Changes  of  considerable  magnitude  were  often  found 
to  have  taken  place  in  the  relative  lengths  of  two  bars  made  of 
different  materials  and  of  large  mass,  even  though  the  reading  of 
the  thermometer  placed  upon  the  surfaces  remained  constant. 
The  presence  of  a  visitor  will  cause  a  rapid  change  of  temperature 
in  a  bar  having  a  large  area  and  a  small  mass.  And  even  if  the 
mass  is  large,  when  there  is  direct  contact  of  the  hands,  an  instan¬ 
taneous  change  in  length  will  follow.  But  if  a  shield  of  thick 
writing  paper  is  interposed,  no  effect  will  be  produced  for  several 
minutes.  Comparisons  were  sometimes  made  in  liquid  glycerine, 
but  generally  in  air. 

In  grinding  end  standard  measures  the  operation  was  per¬ 
formed  first  in  liquid,  to  within  a  thousandth  of  an  inch,  after 
which  comparisons  were  made  with  the  standard  in  air,  extending 
over  a  period  of  from  ten  to  fifteen  days,  and  at  temperatures 
ranging  largely  below  and  above  62°  F.  After  two  or  three 
operations  and  comparisons  have  been  made,  the  true  limit  is 
reached. 

The  net  result  of  the  scientific  and  mechanical  work  expended 
upon  them  at  enormous  cost  is  that  P.  &  W.  i  is  53  millionths 
of  an  inch  longer  than  the  imperial  yard,  and  P.  &  W.  2  is  36 
millionths  of  an  inch  shorter  than  the  imperial  yard  at  62“  F. 
P.  &  W.  3  is  227  millionths  of  an  inch  too  short. 

The  importance  of  temperature  in  standards  may  be  illustrated 
by  the  fact  that  of  the  forty  copies  of  the  British  imperial  standard 
yard  made  for  presentation  to  different  Governments,  only  two  are 
standard  at  60°  F.,  though  all  are  made  of  the  same  alloy — Baily’s 
metal.  But  as  the  coefficients  of  expansion  are  uniform,  com¬ 
parisons  of  these  can  be  made  at  any  temperature,  which  could 
not  be  done  with  materials  having  different  coefficients.  Thus,  if 
a  bar  of  steel  were  compared  with  one  of  Baily’s  metal,  and  both 
were  standard  at  62°  F.,  they  would  not  be  alike  in  length  at 


STANDARDS  OF  MEASUREMENT.  223 

72°  F.,  because  the  brass  would  expand  at  a  higher  rate  than 
the  steel. 

Having  a  bar  ruled  correctly  and  within  only  some  millionths 
of  an  inch  of  absolute  accuracy  on  its  total  length,  this  bar  is  used 
for  the  derivation  of  end  measures.  So  that  the  end  measure,  and 
the  test  contact  are  derived  from  line  measure.  This  might  seem 
almost  to  contradict  the  statement  that  in  the  shops  the  gauge 
system  is  a  more  accurate  one  than  the  rule  system.  But  the 
methods  of  the  shop  do  not  permit  of  the  use  of  microscopes,  and 
the  other  appliances  which  form  part  of  the  readings  and  methods 
of  transference  of  the  comparator. 

An  important  feature  in  the  production  of  standards  for 
measurement  is  that  once  the  ruled  bar  is  made,  it  is  never 
handled  or  touched  in  the  transference  of  dimensions  from  it  to 
the  shop  standards.  How  this  is  done  cannot  be  explained  in  a 
sufficiently  lucid  manner  without  drawings  of  the  machine  the 
comparator — by  which  it  is  accomplished.  But  the  result  is  that 
any  number  of  copies  of  dimensions  can  be  transferred  without 
the  slightest  wear  on  the  original  taking  place.  The  only  possible 
change  which  it  could  undergo  would  be  that  due  to  internal 
strains  in  the  material,  which  is  eliminated  by  careful  annealing  at 
a  temperature  above  that  of  any  temperature  due  to  climate. 

The  grinding  of  end  measures  is  done  by  special  machinery 
by  the  aid  of  a  special  fixture,  the  block  to  the  ground  sliding 
over  a  plane  surface,  in  the  centre  of  which  is  a  copper  plug 
charged  with  emery  or  diamond  dust.  Measurements  are  taken 
from  time  to  time,  and  great  care  is  exercised  to  have  the  tem¬ 
perature  to  correspond  with  that  of  the  ruled  bar  when  making 
these  measurements. 

The  practical  results  are  these:  a  number  of  end  measure 
pieces  of  various  lengths  are  laid  in  a  groove  planed  in  a  massive 
block  of  cast  iron.  One  piece  is  clamped  down  to  form  an  end 
stop,  and  when  the  pieces — seven  or  nine,  or  other  numbers  as 
the  case  may  be,  which  go  to  make  up  12  in. — are  laid  down, 
another  piece  is  laid  down  and  clamped  at  the  other  end.  Then 
the  end  stops  are  readjusted  until  a  4  in.  end  measure  can  be 
just  moved  easily  between  them,  almost  by  its  own  weight.  To 
prevent  contact  of  the  hand  with  this,  and  transference  of  its 
warmth,  it  is  held  by  a  slip  of  wood  inserted  in  a  small  hole  in  the 
piece.  Then  the  pieces  are  removed,  the  end  stops  remaining. 


224 


TOOLS. 


and  another  set  taken  and  inserted,  the  precaution  having  been 
taken  of  laying  them  on  the  cast-iron  block  until  they  arrive  at 
the  same  temperature.  The  insertion  of  the  \  in.  piece  then 
indicates  by  its  slack  or  tight  fitting  the  difference  in  length 
between  the  sets  If  a  difference  occurs,  this,  divided  by  the 
number  of  pieces,  gives  the  average  for  each  piece.  But  to 
ascertain  the  exact  location  of  the  maximum  error  each  piece  can 
be  re-tested  by  the  standard  bar. 

We  will  now  take  up  the  consideration  of  the  various  instru¬ 
ments  which  are  derived  from  the  standards. 

The  common  rule  has  shared  in  the  advances  which  have 
been  made  in  the  practice  of  recent  years,  so  that  with  regard  to 
this  instrument  the  workman,  and  machinist  is  much  better 
equipped  than  formerly.  He  not  only  has  a  much  larger  selection 
of  common  rules,  but  a  wider  range  of  graduations.  Rules  are 
made  in  various  lengths,  widths,  and  thicknesses,  tempered,  and 
flexible,  so  that  they  can  be  used  in  narrow  spaces,  or  bent  round 
curves,  and  to  read  in  English,  or  metric  divisions,  and  of  square, 
and  triangular  section,  besides  other  special  forms.  And  beyond 
these  there  are  the  various  applications  of  the  vernier  to  caliper 
rules,  in  which  the  sense  of  touch  is  combined  with  that  of  sight, 
for  reading  dimensions  for  which  rigidly  fixed  gauges  are  un¬ 
suitable. 

A  machinist  with  only  one  rule  is  not  well  equipped.  His 
principal  rule  should  be  divided  out  chiefly  in  the  measures 
which  he  habitually  uses,  and  be  of  a  length  most  suitable  for  the 
class  of  work  which  he  chiefly  handles.  It  is  rather  confusing  to 
have  a  kind  of  universal  rule  with  all  sorts  of  subdivisions,  just  as 
it  is  to. have  universal  scales,  or,  as  in  the  case  of  the  pattern¬ 
maker,  to  have  both  standard  divisions,  and  those  also  for  con¬ 
traction  for  iron,  steel,  and  brass,  on  one  rule.  Mistakes  are 
liable  to  occur,  and  do  happen,  besides  which  time  is  lost  in 
locating  the  class  of  divisions  required.  It  is  better  to  have  rules 
divided  similarly  down  the  whole  of  one  side,  and  with  four  sets 
of  graduations,  two  on  each  side,  and  all  in  the  same  class  of 
measurement — inches  or  millimetres,  eighths,  or  tenths,  &c.  For 
instance,  tenths,  twentieths,  and  their  subdivisions  are  seldom 
wanted  in  our  shops ;  metric  divisions  are  still  only  used  to  a 
limited  extent.  It  is  better,  therefore,  to  have  the  principal  rule 
divided  only  into  eighths  and  their  aliquot  subdivisions,  and  a 


STANDARDS  OF  MEASUREMENT. 


225 


separate  rule  for  millimetres,  and  another  for  tenths.  The 
principal  rule,  again,  should  be  no  longer  than  is  suited  to  the 
general  run  of  work,  and  is  most  convenient  when  it  can  be 
slipped  into  the  waistcoat  pocket ;  hence  the  popularity  of  the 
6  and  4  in.  rules.  A  12  in.  rule  means  the  rule  pocket  in  the 
trousers,  though  in  working  continually  at  the  marking-off  table  or 
other  fixed  location  the  rule  need  not  be  carried  about  at  all. 

Then,  again,  there  is  a  wide  choice  in  the  types  of  rules,  apart 
from  the  question  of  their  subdivision.  They  may  be  wide  or 
narrow,  rigid  or  flexible.  Narrow  rules  are  very  handy,  inasmuch 
as  they  fulfil  similar  functions  to  depth  gauges,  as  do  the  brass 
slides  in  the  slide  rules.  Thin  rules  of  tempered  steel  go  round 
curves  better  than  thick  rigid  ones.  Besides  these,  specially 
flexible  rules  are  made  of  spring  tempered  steel.  There  are  others 
which  are  less  used,  but  which  help  to  make  up  the  wealth  of 
rules  now  offered  to  the  machinist  and  erector. 

Though  in  these  days  of  gauged  work  the  functions  of  the 
rule  have  been  largely  invaded,  the  duties  of  considerable  numbers 
of  men  being  such  that  a  rule  is  scarcely  ever  required  or  used  by 
them,  for  the  general  hand  this  instrument  is  as  much  in  request 
as  ever.  There  is  plenty  of  work  for  which  the  gauges,  micro¬ 
meters,  and  allied  instruments  are  of  no  service.  In  all  the  work 
of  the  carpenter,  joiner,  and  allied  trades,  of  the  marker-off,  of 
the  erector  and  millwright,  large  sections  of  that  of  the  turner, 
planer,  and  shaper,  and  slotter  hands,  and  much  of  that  of  the 
fitter,  common  rules,  calipers,  and  compasses  fulfil  the  chief 
functions.  By  the  use  of  finely  graduated  steel  rules,  and  fine 
adjustment  compasses  and  calipers,  the  greatest  volume  of  the 
general  work  of  enginers’  shops  is  still  done. 

The  rule,  again,  is  often  incorporated  with  other  appliances, 
notably  the  common  square.  From  the  wooden  try  squares  of 
the  carpenter,  and  patternmaker,  thus  divided  out,  the  high-class 
graduated  steel  squares  have  been  derived.  These  are  valuable 
to  the  marker-off  and  fitter  and  to  the  machine  hands.  Mill¬ 
wrights  and  erectors  find  them  of  great  value  in  getting  heights  of 
centres,  simultaneously  with  squaring  up.  In  many  squares  the 
outside  edges  only  of  the  blade  are  graduated,  as  when  the  stock 
is  thick  and  the  blade  thin.  This  follows  the  earlier  forms  ;  but 
in  the  later  and  more  complete  squares  that  are  specially  made 
for  machinists  and  fitters,  in  which  the  blade  and  stock  are  of  the 

p 


226 


TOOLS, 


same  thickness,  one  outer  and  one  inner  edge  is  graduated.  In 
some  instances  all  four  edges  are  graduated,  an  inside  and  outside 
edge  having  similar  graduations,  and  both  faces  being  alike 
divided. 

The  slide  caliper  rules  are  another  application  of  the  common 
rule.  But  they  render  the  use  of  common  calipers  for  the  trans¬ 
ference  of  dimensions  unnecessary,  since  the  tongue  is  graduated 
in  addition  to  the  ordinary  graduations  on  the  edges  of  the  blade. 
These  are  made  in  different  designs,  one  having  a  tongue  sliding 
in  the  body  of  the  blade,  another  having  a  slide  adjustable  along 
the  lower  edge  of  the  blade. 

The  common  rule  is  an  instrument  that  is  too  often  very  badly 
served.  It  is  used  to  scrape  chips  and  dust  off  the  surfaces  of  work 
in  machines,  to  probe  the  depths  of  holes  and  recesses.  It  is 
allowed  to  rust,  and  then  polished  with  emery  cloth.  It  is  em¬ 
ployed  as  a  rough  straight-edge  on  castings  and  forgings,  is  thrust 
between  joints  to  see  how  wide  they  are  apart,  sometimes  emery 
cloth  is  wrapped  around  it  for  polishing.  And  thus  the  end 
wears,  the  edges  become  rounding,  and  fine  divisions  become 
indistinct.  Rule  measurement,  never  the  most  precise  in  shop 
practice,  thus  becomes  unreliable.  When  the  end  becomes  worn, 
accurate  measurement  cannot  be  started  from  the  end.  -  If  the 
edge  is  convex,  the  divisions  do  not  reach  to  the  edge,  and  then 
the  rule  cannot  be  used  by  its  edge  with  perfect  accuracy. 

When  the  end  of  a  rule  has  not  been  worn  by  long  service,  or 
by  abusive  treatment,  it  affords  a  very  ready  means  of  taking 
measurement  from,  provided  there  is  a  shoulder  against  which 
the  rule  can  be  set,  and  from  which  the  dimension  can  be  taken. 
If  the  measurement  starts  from  an  edge,  the  rule  is  abutted 
against  a  straight-edge  or  blade  of  a  square  set  up  against  the 
edge.  The  same  method  is  of  course  even  more  essential  when 
an  edge  is  rounded.  The  Starrett  Company  make  a  rule  to  suit 
such  cases.  It  has  a  short  return  piece  or  hook  at  the  end, 
pivoted  on  an  eccentric  stud,  and  which  can  be  removed  when 
not  required.  Such  a  rule  is  valuable  for  setting  internal  calipers 
by,  and  especially  for  measuring  from  internal  shoulders  in  bores, 
or  planed  slots  with  recesses. 

The  way  to  use  a  rule  is  either  on  the  depth-gauge  principle — 
that  of  starting  to  read  from  the  end, — or  the  edge  of  the  rule  is 
laid  upon  the  work  and  the  dimension  read  off,  or  marked  from 


STANDARDS  OF  MEASUREMENT. 


227 


divisions  intermediate  from  the  end.  The  latter  is  the  safer  and 
the  better  method  to  adopt  generally.  Although  the  eye  has  to 
judge  of  the  coincidence  or  otherwise  of  two  divisions  on  the 
rule  in  the  latter  instance,  against  one  only  in  the  former,  the 
finest  results  are  attainable  when  the  lines  of  division  are  set 
upon  the  work,  the  rule  being  held  edgewise.  Working  to 
the  “  thickness  of  a  line  ”  is  a  very  elastic  expression  \  it  is  really 
a  minute  amount  when  the  lines  on  the  best  steel  rules  are 
worked  by. 

External  calipers  are  set  easily  enough  from  the  end  of  a  rule ; 
internal  ones  are  generally  set  from  one  end,  or  from  an  external 
pair.  To  set  them  from  one  end,  the  rule  is  stood  on  end  on 
a  block  of  metal,  as  is  also  the  lower  leg  of  the  caliper.  Or  it  is 
set  horizontally  against  a  vertical  face.  It  is  not  easy  to  get 
exact  dimensions  with  internal  calipers  when  set  on  two  divisions 
on  the  body  of  the  rule,  unless  the  points  are  narrow  and  quite 
true  and  parallel. 

Scales  do  not  come  into  the  hands  of  the  machinist  and  fitter 
nearly  so  often  as  they  did  formerly.  They  are  now  mainly  used 
in  the  drawing  offices,  and  pattern  shop.  The  reason  of  this 
change  is  the  gradual  diminution  of  the  practice  of  making  small 
scaled  drawings  for  the  workshops,  to  which  the  supersession  of 
drawings  by  sun-printed  copies  has  mainly  contributed.  In  the 
days  when  drawings  and  tracings  made  by  hand  were  in  sole  use, 
the  supply  was  limited  by  their  costliness.  Drawings  and  mounted 
tracings  were  then  made  to  small  scales.  Often,  all  classes  of 
work  belonging  to  the  different  shops  were  included  in  one 
drawing,  or  mounted  tracing,  which  went  the  round  of  all  the 
shops,  and  from  which  selection  was  made  for  the  work  in  each 
department,  until  at  last,  sadly  dilapidated,  and  greasy  and  obscure, 
it  found  its  resting-place  again  in  the  office  drawers.  Those  were 
the  days  when  the  scale  was  a  necessity;  to  the  foot  was  very 
common — ^  in.  on  the  foot  rule  read  i  in.  in  the  work ;  3  in.  to 
the  foot,  or  quarter  size,  was  also  common;  i,  i;^,  and  2^  in. 
were  less  used,  but  i  and  |  in.  were  largely  employed  for  general 
drawings.  Hand  sketches  made  on  section  paper  supplemented 
these  drawings — often,  in  fact,  were  substituted  for  them,  though 
not  made  for  scaling  by.  Now  the  usual  practice  is  to  reserve  the 
small  scales  for  general  drawings  only,  and  to  make  detail  drawings 
and  prints  for  shop  use  to  large  scales  or  to  full  size,  and  often 


228 


TOOLS. 


also  fully  dimensioned  though  drawn  to  full  size,  so  that  scaling  is 
rendered  quite  unnecessary. 

A  scaled  dimension  is  never  taken  from  an  end,  but  is  by 
lines  of  division  only,  the  scale  being  held  edgewise  on  the 
drawing.  To  avoid  this  tilting  up  is  the  reason  for  making  some 
scales  of  triangular  section,  allowing  the  reading  of  the  scale  to  be 
taken  without  lifting  it  up  from  the  paper.  In  one  type  the  actual 
faces  are  lifted  slightly  from  the  paper  by  end  pieces,  to  avoid 
wearing  the  graduations. 

The  forms  and  materials  of  scales  include  those  of  boxwood, 
of  double  convex  section,  very  flat  in  their  curves,  or  of  chamfered 
sections,  the  paper  scales,  and  the  triangular-shaped  ones  of 
boxwood  or  metal,  and  some  special  forms. 

The  objection  to  the  boxwood  scales  is  that  the  edges  become 
damaged  with  wear,  that  the  wood  is  slightly  affected  by  changes 
in  temperature,  and  that  they  are  not  flexible  enough  to  permit  of 
measuring  round  curved  lines.  Paper  scales  are  better  adapted 
to  the  latter  conditions,  but  they  soon  lose  their  graduations 
unless  protected  when  new  with  an  application  of  clear  varnish. 
Metallic  scales  do  not  wear  so  readily,  but  temperature  affects 
them. 

Universal  scales  are  undesirable,  being  a  fruitful  source  of 
mistakes.  A  set  of  scales  is  properly  necessary,  each  one  of 
which  has  four  sets  of  graduations,  one  only  on  each  edge,  as 
f,  I,  1 1  in.,  or  other  divisions  alike  all  down  one  side,  and  the  end 
ones  only  subdivided,  to  permit  of  reading  two  scales  on  one  edge, 
as  f  and  i|  in.,  and  so  on. 

Steel  tapes  are  used  by  some  classes  of  erectors  and  fitters 
where  long  dimensions  come  in.  They  are  useful  in  locating 
centres  of  bearings,  for  shafting,  and  heights.  In  cases  where 
diameters  of  large  dimensions  are  required,  and  rods  or  other 
objects  occupy  the  central  portions,  a  steel  tape  is  useful  for 
measuring  round  an  external  circumference  by,  and  thence 
deducing  diameters.  They  are  also  valuable  for  setting  out 
dimensions  for  the  erection  of  work  of  large  size. 

But  in  the  greater  number  of  measurements  of  considerable 
length  in  workshops,  preference  is  given  to  a  rigid  rod  of  wood,  on 
which  the  lengths  required  are  marked.  Yellow  pine,  straight  in 
grain  and  well  seasoned,  does  not  shrink  endwise  to  any  appreci¬ 
able  extent.  To  mark  off  lengths  on  such  rods — end  measure- 


STANDARDS  OF  MEASUREMENT.  229 

ment  not  being  as  a  rule  employed — a  standard  rod  is  used.  If 
lengths  are  marked  from  a  rule  of  i  ft.  or  2  ft.  in  length,  error  is 
certain  to  arise  in  the  aggregate  length,  hence  the  advantage  of 
standard  rods.  The  method  that  has  answered  well  in  the  writer’s 
experience  is  this : — A  standard  rod  is  purchased  of  a  mathe¬ 
matical  instrument  maker,  either  5  or  10  ft.  in  length,  divided 
finely  on  the  first  foot,  and  inch,  on  a  brass  plate  let  into  the 
wood,  and  having  each  foot  marked  on  a  brass  plate  let  into  the 
wood.  This  is  kept  in  a  box  for  reference.  From  this  a  rod  is 
made  for  each  shop,  and  from  the  latter  the  men  mark  the  lengths 
they  require,  or  check  lengths  taken  on  their  working  rods.  This 
method  is  invaluable,  avoiding  not  only  slight  errors,  but  also 
often  big  mistakes.  The  principal  standard  is  never  worn  by  use, 
yet  it  remains  a  permanent  reference  and  court  of  appeal. 


CHAPTER  XX. 


Squares,  Surface  Plates,  Levels,  Bevels,  Protractors,  &c. 

Origination  of  Straight-edges — Care  of — Surface  Plates — Flexure — Plates  for 
Standard  Reference  —  Large  Straight-edges — Winding  Strips — Squares — 
Try  Squares — Testing  of — Method  of  Making — Combination  Squares — 
Centre  Squares  —Bevels — Bevel  Protractors — Scale  of  Chords — Set  Squares 
— Levels — Wear  of— Various  Forms — Plumb  Bobs. 

^  1  ''HE  straight-edges,  squares,  bevels,  protractors,  and  spirit 
I  levels,  though  not  strictly  tools  used  in  measurement,  are 
nevertheless  directly  and  constantly  associated  with  the 
actual  methods  of  measurement. 

The  truth  of  surfaces  and  the  correct  relations  of  surfaces  to 
each  other  have  to  be  checked,  along  with  their  distances  apart ; 
and  in  setting  work  for  tooling  or  for  erecting,  the  exact  horizontal, 
or  vertical  truth  of  surfaces  has  to  be  assured.  In  the  construc¬ 
tion  of  these  instruments  a  different  set  of  problems  comes  in 
from  those  which  have  hitherto  been  considered.  Though  in 
these,  as  in  measurement,  absolute  accuracy  is  not  attainable,  a 
very  close  approximation  thereto  is  sufficient  for  all  working 
requirements. 

A  feature  of  the  straight-edges,  in  which  they  differ  from  the 
majority  of  measuring  tools,  is  that  they  can  be,  and  frequently 
are,  made  in  the  shops  by  the  workmen.  The  same  remark 
applies  to  surface  plates.  There  are  two  methods  by  which  these 
can  be  produced.  They  are  either  made,  and  tested  by  another 
edge,  or  plate  known  to  be  true,  or  they  are  originated  without 
reference  to  any  existing  instrument.  Origination  is  effected  by 
mutual  correction  of  surfaces. 

To  originate  straight-edges,  three  separate  edges  must  be 
obtained,  any  one  of  which  will  coincide  perfectly  with  either  of 
the  other  two.  The  problem  is  exactly  the  same  as  that  of  surface 
dlates.  It  seems  easy  to  realise  such  accuracy ;  it  is  difficult  of 


STRAIGHT-EDGES  AND  SQ DARES.  231 

attainment  in  practice,  and  it  can  only  be  secured  by  most  careful 
and  minute  application  of  the  scrape  in  the  final  stages  of 
correction. 

It  is  obvious  that  though  two  surfaces  may  be  brought  into 
perfect  mutual  contact,  there  is  not  only  no  certainty,  but  a  great 
improbability,  that  they  will  be  true  planes,  since  they  may  have 
equal,  and  opposite  amounts  of  concavity,  and  convexity,  or  of 
general  inequalities.  But  if  three  surfaces  are  in  perfect  mutual 
contact  they  must  be  true  planes,  since  it  is  inconceivable  that 
they  can  be  otherwise.  The  method  of  origination,  therefore,  is 
to  get  three  approximately  true,  either  by  planing  or  filing,  and 
then  check  them  in  pairs.  When  two,  say  Nos.  i  and  2,  are 
tried  together  and  show  no  light  or  want  of  contact  between  in 
reversed  positions,  the  third  is  tried  with  one  of  them,  say  No. 
I,  in  one  direction  and  reversed.  These  will  not  agree,  and  so 
correction  is  effected  until  they  do.  Then  No.  3,  thus  corrected. 


is  tried  against  No.  2,  and  this  process  is  continued  until  any  one 
straight-edge  coincides  with  both  of  the  other  two. 

Having  once  obtained  a  true  surface,  however,  the  work  of 
origination  need  not  be  repeated,  unless  the  accuracy  of  the 
surface  becomes  impaired.  Generally,  in  shops,  a  surface  plate 
forms  the  standard  of  reference,  or  a  large  cast-iron  straight-edge. 
If  these  are  treated  carefully,  they  retain  their  accuracy  for  an 
indefinite  period,  but  not  if  they  are  employed  for  rough  testing 
of  instruments,  or  if  they  are  allowed  to  become  dusty  and  dirty. 
Wooden  covers  are  provided  in  shops  where  the  necessity  for 
proper  care  is  recognised,  and  these  should  be  always  kept  on, 
excepting  when  the  plates  are  in  use.  Fig.  292  shows  a  section 
through  a  plate  so  covered.  The  ribbing  seen  is  never  omitted 
from  any  plate,  whether  it  measures  2  ft.  or  only  8  in.  across.  It  is 
necessary  in  order  to  prevent  risk  of  flexure,  the  slightest  degree 
of  which  would  be  fatal  to  the  utility  of  the  plate.  The  arrange¬ 
ment  of  the  ribs  is  varied  in  different  designs,  a  very  frequent  form 


TOOLS. 


232 

being  that  with  diagonal  crossing  ribs,  instead  of  parallel  ones,  as 
in  the  illustration.  Flexure  is  further  guarded  against  by  providing 
three  nibs  on  the  bottom  of  the  ribs,  so  that  the  plate  has  a  three- 
point  bearing,  which  will  stand  on  an  uneven  surface  without 
distortion.  This  is  most  important  in  large  plates,  which  if 
provided  with  four  points  of  support  are  almost  sure  to  become 
winding.  Large  plates  are  generally  oblong  in  form  ;  small  ones 
are  square,  or  circular.  But  it  is  much  better  to  have  them 
square  than  round,  because  the  edges  can  be  used  for  squaring 
from,  as  in  testing  try  squares. 

Another  point  is  that  certain  plates,  and  straight-edges  should 
be  kept  for  standard  reference,  distinct  from  those  which  are 
employed  for  the  common  service  of  the  shops.  Small  plates  are 
generally  supplied  for  the  use  of  individual  men,  or  groups  of  men, 
and  are  kept  on  the  benches  or  machines.  These,  of  course, 
cannot  be  preserved  for  reference,  and  their  accuracy  is  bound  to 
become  impaired  in  time.  But  standards  can  be  retained  in  the 
tool-room,  or  in  the  foreman’s  office,  just  as  standard  gauges  are 
kept  for  reference  only. 

Surface  plates  are  frequently  used  for  work  that  lies  outside 
their  legitimate  functions,  chief  among  these  in  the  lining-out  of 
work,  and  the  checking  of  the  relations  of  pieces  of  work.  A 
marking-off  table,  or  a  plain  plate  which  is  planed  only,  without 
scraping,  is  accurate  enough  for  duty  of  this  kind,  so  retaining  the 
the  surface  plates  for  their  proper  function — that  of  checking  the 
truth  of  surfaces  which  are  receiving  their  final  corrections  by  the 
scrape. 

The  foregoing  is  not  the  present  manufacturing  method 
employed  for  straight-edges.  Scraping  must  be  employed  in  the 
final  stages  for  exact  corrections  of  the  broad  surfaces  of  surface 
plates,  just  as  it  is  in  machine  slides,  work  from  which  no  grinding 
machine  has  yet  displaced  the  scrape.  But  there  is  a  great 
difference  between  a  broad  surface  and  an  edge.  The  small 
straight-edges  which  are  made  commercially  are  ground  true  along 
the  edges,  and  are  therefore  made  cheaply  ;  and  there  is  the  advan¬ 
tage  that,  being  ground,  they  are  hardened  on  the  edges  previous 
to  grinding,  which  preserves  their  durability  for  a  much  longer 
period  than  if  left  soft. 

Large  straight-edges  are  not  made  of  steel,  but  of  cast  iron,  and 
these  are  nearly  invariably  finished  by  scraping.  In  these  large 


STRAIGHT-EDGES  AND  SQUARES. 


233 


sizes,  length  and  weight  cause  trouble  by  rendering  them 
awkward  to  handle,  and  by  the  tendency  to  flexure.  The  typical 
form  made  is  that  shown  in  Fig.  293,  by  which  these  evils  are 
reduced  to  a  minimum.  Frequently  circular  lightening  holes  are 
cast  instead  of  the  oblong  ones  shown,  and  two  feet  also  are  often 
added. 

In  handling  these  large  tools  for  testing  machine  beds  and 
slides  while  scraping  is  in  progress,  it  is  generally  more  convenient 
to  suspend  the  straight-edge  in  a  hoist  or  light  crane,  and  to  lower 
it  on  the  work  for  testing,  after  which  it  is  swung  away  until 
required  again.  This  is  obviously  the  only  practicable  method 
with  heavy  machine  beds.  But  where  the  work  being  scraped  is 
comparatively  small,  the  straight-edge  may  be  supported,  and  the 
work  turned  over  on  it  for  testing. 

Contact  between  straight-edges  and  the  work  is  tested  by  red 
lead,  or  by  sighting  between  tbe  two  faces.  Either  method 


Fig.  293. 


enables  a  workman  to  detect  a  very  minute  departure  from  coin¬ 
cidence,  but  the  lead  leaves  a  record  on  the  work. 

It  is  not  allowable  to  rub  a  straight-edge  hard  on  the  work,  as 
is  sometimes  done  with  the  surface  plate,  the  straight-edge  being 
too  elastic  and  yielding,  so  giving  a  false  test.  A  straight-edge 
must  be  held  quite  perpendicularly,  or  normal  to  the  plane  of  the 
work,  as  a  little  inclination  therefrom  may  falsify  results. 

A  straight-edge  is — except  in  the  largest  ones  of  cast  iron 
made  with  both  edges  parallel  and  true.  Either  edge  can  be  used, 
and  there  is  the  advantage  that  a  level  can  always  be  laid  on  the 
uppermost  edge.  This  is  valuable  when  setting  work  on  machines, 
and  when  erecting.  It  is  very  serviceable  both  when  the  surface 
is  a  comparatively  rough  and  uneven  one,  and  also  when  facings 
occur,  across  which  the  straight  edge  is  bridged.  It  is  also  useful 
in  order  to  take  a  vertical  dimension  between  two  faces,  one  of 
which  stands  above  or  below  another,  and  situated  at  a  distance 
away.  These  are  cases  that  frequently  occur.  Unless  faces  are 
perfectly  true,  it  is  obvious  that  the  straight-edge,  if  laid  on,  will  be 


234 


TOOLS. 


thrown  out  thereby,  and  the  error  will  be  considerable  where 
multiplied  by  the  length  of  the  straight-edge.  In  such  cases  the 
level  gives  the  average  or  general  level  of  the  facing  or  of  the 
work,  Internal  faces,  bores,  &c.,  can  be  checked  in  a  similar 
way. 

A  particular  application  of  straight-edges  is  that  of  two  being 
used,  of  the  same  dimensions,  termed  winding  strips,  for  testing 

the  accuracy  or  otherwise  of  a  surface 
intended  to  be  plane.  They  are  laid  as 
shown  in  Fig.  294,  and  a  sight  is  taken 
along  their  upper  edges,  when  it  is  easy 
to  detect  any  minute  departure  from 
accuracy.  These  are  employed  both  by 
wood  and  metal-workers,  and  in  the 
foundry  for  levelling  beds  of  sand. 

Squares  may  be  considered  as  two  straight-edges  rigidly  set  at 
right  angles,  since  it  is  essential  that  the  edges  be  true.  So  much 
work  requires  squaring  that  these  tools  are  made  in  two  types — the 
try  square,  and  the  set  square, — and  each,  in  several  sizes,  becomes 
a  necessary  portion  of  the  equipment  of  a  workman  both  at  bench, 
vice,  and  machine. 

A  try  square  generally  has  the  stock  thicker  than  the  blade,  for 
convenience  of  being  able  to  set  the 
stock  against  an  edge  when  squaring  i  i 

over,  or  down.  When  the  two  are  j  i 

of  the  same  thickness,  the  instru-  i  ! 

ment  can  only  be  properly  used  as  j  j 

a  set  square,  that  is,  be  laid  upon  ! 

one  outside  edge,  testing  by  the  • 

other  outside  edge.  Or  the  inner  _ | 

edges  can  be  used  for  checking  [  j]J _ 

work  already  brought  into  an  pig.  295. 

approximately  square  relation,  but 

not  for  marking  lines  by  from  an  edge  laid  across  a  face. 

In  checking  edges  it  is  very  essential  that  the  blade  of  the 
square  be  kept  perpendicular  with  the  edge  being  tested.  If  thrown 
over,  any  slight  lack  of  truth  in  the  blade  itself  will  falsify  the  test. 

Squares  can  be  easily  tested  by  laying  one  edge — that  of  the 
stock — against  a  true  base,  marking  a  line  by  the  edge  of  the  blade 
and  then  turning  the  square  right  round,  and  testing  the  same  edge 


Fig.  294. 


235 


STRAIGHT-EDGES  AND  SQUARES. 

by  the  same  line  (Fig.  295).  Any  departure  from  a  true  right  angle 
in  the  square  will  then  be  apparent,  being  just  doubled. 

The  usual  method  of  making  try  squares  is,  after  having  pre¬ 
pared  the  blade,  and  the  stock,  just  as  separate  straight-edges  would 
be  prepared,  to  cut  a  saw  kerf  in  the  stock,  finishing  the  cut  with  a 
narrow  file  to  admit  the  blade.  Having  then  set 
the  blade  square,  holes  are  drilled  for  rivets,  and 
one  rivet  after  another  is  inserted,  checking  the 
truth  of  the  blade,  and  making  any  necessary  cor¬ 
rections  as  each  rivet  is  closed. 

There  is  a  disadvantage  in  this  old  practice, 
inasmuch  as  any  future  corrections  of  the  stock  and 
blade  have  to  be  done  with  the  parts  fast  together. 

Corrections  become  necessary  at  intervals,  because 
the  inner  face  of  the  stock  and  the  inner  blade 
edge  wear  more  next  the  inner  angles,  than  near 
the  outer  portions.  Moreover,  squares  become 
damaged  by  falling  on  the  ground,  or  by  articles 
dropping  on  them.  It  is  convenient,  then,  to  be  able  to  take  t  e 
blade  and  stock  apart  for  correction.  This  can  be  done  when  the 

fittings  are  those  shown  in  Figs.  296  to  301. 

Fig.  296  is  a  section  through  a  square  in  which  the  blade  fits 
into  a  slot.  But  instead  of  using  rivets,  which  do  not  permit  of 


Fig.  296. 


• 

S)  "s' 
(S  ® 

Fig.  297. 


after-adjustment,  a  special  form  of  screw  a  is  employed.  It  is  split 
through  a  portion  of  its  length,  and  expanded  by  the  tapering  screw 
B  inserted  in  its  centre.  The  act  of  tightening  the  screw  pulls  the 
blade  against  the  shoulder  of  the  stock  by  the  very  familiar  device, 
used  in  cottared  work,  of  leaving  slight  clearances  at  a  and  A 

The  form  of  square  which  has  some  advantages  in  manufacture 


236 


TOOLS. 


over  the  old  central  blade  type  is  shown  in  Fig,  297,  in  which  the 
blade  fits  into  a  recess  cut  in  one  face  of  the  stock.  Various 
methods  of  fastening  these  are  shown  in  subsequent  figures.  Fig. 


Fig.  298. 


Fig.  299. 


298  shows  the  screw  and  the  split  expanding  busk  in  section,  and 
the  dotted  lines  are  introduced  to  show  the  effect  of  tightening 
the  screw,  in  cottar  fashion,  the  pressure  along  the  edge  a  tending 
to  force  the  stock  over  at  b.  The  amount  of  spring  is  extremely 

minute,  but  sufficient  to  provide 
an  elastic  force  which  keeps  the 
blade  well  up  to  its  shoulder. 

Fig.  299  shows  the  method  em¬ 
ployed  in  large  squares,  in  which, 
in  addition  to  the  special  screw  in 
the  centre,  four  common  screws  are 
put  in  near  the  corners  to  reinforce 
the  work  of  the  central  one. 

Figs.  300  and  301  illustrate 
methods  of  fitting  with  common 
tapering  screws,  not  split,  but  which 
draw  the  blade  up  as  already  men¬ 
tioned.  These  are  a  B.  &  S.  device. 

Fig.  302  shows  another  type  of  square,  the  Starrett,  in  which 
the  stock  and  blade  can  not  only  be  taken  apart,  but  can  also  be 
adjusted  lengthwise,  which  is  a  very  convenient  adjustment  when 
squaring  work  in  which  a  shoulder  would  interfere  with  a  blade  of 
ordinary  length.  The  blade  has  a  groove,  and  the  stock  a  special 


STRAIGHTEDGES  AND  SQUARES. 


237 


304- 


rig.  306. 


238 


TOOLS. 


clamping  bolt  and  nut,  with  milled  head,  which  permits  of  short¬ 
ening  or  lengthening  the  amount  of  projection  of  the  blade  at 
either  end  out  from  the  stock.  See  the  section.  Fig.  303. 

In  many  instances  the  blades  of  squares  are  divided  into  inches 
and  parts,  which  are  convenient  for  measuring  depths  or  lengths 
simultaneously  with  squaring  over  or  up. 

Fig.  304,  A,  B,  and  c,  shows  a  home-made  combination  square, 
which  is  formed  by  the  attachment  of  two  flat  squares  with  a  strap, 
provided  with  a  milled-headed  screw,  pressing  upon  a  washer  strip. 
There  are  many  possible  ways  of  clamping  the  two  squares  to¬ 
gether,  three  only  of  which  are  shown.  A  depth  gauge  is  pro¬ 
duced  when  the  two  are  back  to  back,  as  in  a  ;  held  in  the  same 
manner,  but  turned  upside  down,  a  shoulder  gauge  is  formed  b, 
while  if  one  square  is  placed  within  the  other,  a  caliper,  or  thick¬ 
ness  gauge  is  the  result  c.  There  are  many  other  combinations 
of  this  useful  tool,  which  can  easily  be  imagined. 

The  centre  squares  are  a  very  useful  alternative  to  dividers,  for 
finding  the  centres  of  circles.  The  patternmaker,  and  woodworker 

employs  that  in  Fig.  305,  consisting  of 
a  piece  of  wood  of  suitable  form,  pro¬ 
vided  with  two  pegs,  which  coerce  the 
square  around  the  edge  of  the  disc 
being  centred.  Short  lines  are  scribed 
across  the  vicinity  of  the  centre,  and 
when  the  square  has  been  shifted 
around  three  or  more  times,  the  inter¬ 
section  of  the  lines  provides  the  centre. 
The  same  class  of  tool,  but  in  metal, 
is  shown  in  Fig.  306,  where  instead  of 
the  pegs,  the  head  itself  forms  an  angle,  the  sides  of  which  make 
contact  with  the  circle,  while  the  straight-edge  screwed  to  the 
head,  cuts  across  the  centre.  Another  form,  made  for  attachment 
to  a  splined  rule,  of  the  type  shown  in  Fig.  302,  is  shown  in 
Fig.  307,  and  it  transforms  the  rule  into  a  centre  square  for  the 
time  being. 

Set  squares  are  not  used  so  much  by  machinists,  as  in  the 
drawing  office,  and  pattern  shop,  and  woodworking  trades,  the 
try  square  being  as  often  as  not  used  as  a  set  square ;  but  they 
form  a  portion  of  the  equipment  of  the  machinist  and  fitter. 

To  the  proper  utility  of  the  set  squares,  the  taking  of  fixed 


239 


STRAIGHT-EDGES  AND  SQUARES. 

angles  is  added,  as  30“,  and  6o“,  or  45“-  These  angles  are  wanted 
so  frequently  that  time  is  saved  by  having  them  combined  with 
set  squares.  For  other  angles,  the  bevel,  or  bevel  square,  is 
employed.  The  function 
of  this  lies,  however,  more 
in  the  testing  of  angles 
that  are  already  brought 
into  approximate  rela¬ 
tions,  than  in  the  setting 
out  of  angles.  Or  they  are 
used  for  taking  the  angles 
from  a  protractor,  and  lay¬ 
ing  them  out  on  the  work. 

Sometimes  one  sees 
common  rules  divided 
into  angles  at  the  knuckle 
joint,  d'hese  should  never 
be  employed  excepting  for 
the  roughest  class  of  out¬ 
door  timber  work,  for 
which  they  are  handy. 

The  principle  is  bad,  to 

use  a  very  small  radius  of  1  •  u 

graduations  in  order  to  obtain  angles  for  lines  several  inches  or 
Lt  in  length,  and  it  cannot  be  done  accurately  in  practice, 
however  great  the  care  taken  in  setting. 

Squares,  bevels,  and 
straight-edges  render  them¬ 
selves  adaptable  to  many 
useful  combinations.  Bevels 
are  made  in  various  forms, 
both  simple,  and  in  combina¬ 
tion  with  protractors.  The 
common  bevel  in  which  the 
blade  is  straight  and  the  slot 
down  the  centre,  lacks  range, 
because  the  edge  a.  Fig.  308,  comes  out  a  considerable  distance 
down  the  stock.  To  avoid  this  is  the  reason  of  the  design  m 
Fig.  309,  in  which  the  blade  has  an  offset  at  one  end,  so  permit¬ 
ting  the  taking  of  the  most  acute  angle  right  from  the  end  of  the 


Fig.  308. 


240 


TOOLS. 


blade.  Besides  this,  the  open  slot  which  occurs  in  the  ordinary 
stock  is  filled  in  on  the  side  next  the  blade  in  Fig.  309?  The 
advantage  of  this  is  that  thin  templets  can  be  laid  on  the  stock 

directly  beneath  the  blade, 
which  cannot  be  done  when  the 
stock  is  pierced  right  through. 

In  one  form  of  bevel,  Fig. 
310,  the  stock  is  slotted  as  well 
as  the  blade,  so  permitting  of  a 
wider  range  of  adjustment  than 
the  common  form  does. 

The  familiar  combination 
bevel.  Fig.  311,  can  be  used  in 
the  same  way  as  the  ordinary 
form,  or  double  by  the  addition 
of  the  auxiliary  blade  a.  The 
blades  can  be  clamped  at  any 
angle  by  the  knurled  nuts,  and 
the  three  blades  used  in  an  in¬ 
finity  of  combination  for  turning 
gear-wheel  blanks,  planing  vees, 
&c.  Its  range  of  utility  is  in¬ 
creased  by  grinding  the  ends  of 
the  blades  to  definite  angles,  so  fulfilling  the  functions  of  set 
squares.  In  one  design  the  slots  are  pierced  through  two  blades ; 
in  the  other,  shown  in  P'ig.  311,  one  blade  only  is  slotted,  the 
others  being  vee  grooved  and  having  bolts  which  fit  these  grooves. 


Protractors,  or  bevel  protractors,  are  tools  in  which  the  angles 
are  measured,  or  set  off  exactly  in  degrees.  There  are  many  forms 
of  these.  Besides  these,  there  are  combination  tools  in  which 


STRAIGHT-EDGES  AND  SQUARES. 


241 


rule,  square,  mitre,  bevel,  and  protractor  are  embodied.  In  the 
common  brass  protractor  supplied  with  mathematical  instruments, 
the  base  is  very  short,  and  leads  to  error  in  setting— error  that 
becomes  magnified.  Though  suitable  for  small  angles,  it  should 
not  be  employed  for  large  drawings.  In  setting  out  the  sections 
of  large  bevel  gears,  for  instance,  an  error  of  a  degree  or  two 
might  easily  be  made  from  the  protractor  to  the  major  diameters, 
and  this  would  produce  a  very  gross  error  in  results.  The  aim 
should  be,  therefore,  as  in  other  departments  of  practice,  to  have 
a  basis  as  large  as,  or  larger  than,  the  work  to  be  laid  out,  so  that 
error  shall  be  minimised  instead  of  magnified. 

In  the  Brown  &  Sharpe  protractor,  Figs.  312  and  313,  the 
blade  a  forms  an  extension  of  a  circular  portion  fitting  by  vee’d 


Fig.  313- 


Fig.  312. 


edges  in  a  frame  b,  of  the  same  thickness.  The  circular  form 
permits  of  the  blade  being  prolonged  inwards  past  the  centre  o 
the  protractor,  so  that  a  line  can  be  drawn,  which  cannot  be 
drawn  when  using  the  ordinary  form.  The  divisions  go  past  90  , 
'and  in  addition  there  is  a' vernier  on  the  frame  which  gives 
readings  to  5',  or  one-twelfth  of  a  degree-another  refinement  on 
ordinary  protractors.  When  the  back  of  the  blade  is  brought 
back  against  the  edge  of  the  frame,  as  at  c,  the  instrument  stands 
at  zero.  The  square  outline  of  the  frame  allows  it  to  be  laid 
against  a  set,  or  try  square  readily,  and  so  often  saves  troub  e. 
The  second  figure  illustrates  the  method  of  insertion  of  the 
central  part  in  the  frame,  into  which  it  is  placed  m  the  manner 
shown,  a  slight  amount  of  spring  being  possible. 


Q 


242 


TOOLS. 


The  Brown  &  Sharpe  universal  protractor,  Fig.  314,  has  its 
stock  extended  towards  one  side,  a  circular  dial  a  is  divided 
round  the  entire  circle,  and  the  divisions  are  protected  by  having 
them  below  the  surface  at  c.  The  dial  turns  on  a  hardened 
central  stud  of  large  diameter.  The  line  of  angle  is  marked  by  a 
straight-edge  b,  which  is  tongued  similarly  to  some  of  the  firm’s 
rules,  so  permitting  it  to  be  slid  longitudinally  in  its  seating,  and 
clamped  independently  of  the  dial. 

The  value  of  very  minute  degrees  of  angle  comes  in  when 
turning  wheel  blanks,  and  when  turning  or  boring  tapers.  These 
almost  invariably  include  minutes  of  angle  as  well  as  degrees,  and 
an  exact  setting  ensures  true  work.  Even  though  work  is  first 


Fig-  314- 


struck  out  correctly,  it  is  convenient  to  check  it  with  a  finely 
graduated  protractor. 

For  the  largest  work  of  a  shop  the  scale  of  chords  is  better 
than  the  small  protractors.  Measurement  can  be  taken  from  a 
sector.  But  a  better  plan  is  to  construct  a  scale  either  in  metal 
or  in  wood.  It  can  be  made  of  any  suitable  dimensions  by  the 
workman  himself,  and  accurate,  in  the  following  way  : — 

Strike  a  quadrant  of  a  circle.  Fig.  315,  and  divide  it  into  90°. 
The  radius  may  be  i,  2,  or  3  ft.  at  pleasure,  according  to  the 
requirements.  Then  take  a  straight-edge  of  boxwood,  or  of  metal, 
gauge  two  parallel  lines  along  it  about  in.  apart.  Fig.  316,  and 
mark  off  between  these  the  exact  length  of  the  chord  of  the 


STRAIGHT-EDGES  AND  SQUARES. 


243 


quadrant ;  that  is,  the  length  of  ihe  straight  line  or  shortest 
distance  between  the  extremes  of  the  90  .  Now,  one  by  one  take 
off  carefully,  first  with  compasses,  and  then  with  trammels  as  the 
distances  increase,  the  chord  lengths  corresponding  with  the 
divisions  into  degrees,  from  the  quadrant,  and  transfer  them  to 
the  line  of  chords  on  the  straight-edge,  always  working  from  one 
end.  For  the  first  15°  or  20°  there  will  be  no  appreciable 
difference  between  the  lengths  of  the 
arcs  and  of  the  chords,  but  after  that 
the  chord  distances  will  begin  to  shorten 
until  the  90°  is  reached.  Square  all 
these  divisions  carefully  across  between 
the  two  lines  gauged  on  the  scale,  and 
these  will  form  a  permanent  instrument 
for  setting  out  angles  by.  To  use  it, 
an  arc  must  be  struck  with  a  radius 
measured  from  zero  to  60°  on  the  line 
of  chords,  on  which  the  angle  required 
will  be  set  out. 

Spirit  levels  are  used  by  machinists  and  fitters  for  levelling 
and  plumbing  work  on  machines  and  in  work  in  course  of  erection. 
The  levels  with  wooden  stocks  are  being  displaced  to  some  extent 
by  those  of  metal,  which  are  less  liable  either  to  become  worn  on 
the  bottom,  or  to  warp.  Levels  are  also  fitted  to  squares,  to  be 
used  when  squaring  up  work  on  machines,  and  in  place.  They 
are  also  fitted  with  provisions  for  adjustment,  and  correction. 

There  was  never  so  great  a  wealth 
of  these  instruments,  in  numer¬ 
ous  types  and  sizes  as  there  is  at 
present. 

Levels  wuth  wooden  stocks  are 
not  the  best  for  engineers’  use, 
though  suitable  enough  for  the  woodworking,  and  building  trades. 
They  are  not  so  suitable  for  moulders,  either,  as  the  metal  ones, 
because  the  sand  soon  roughens  up  the  bottom,  and  impairs  their 
accuracy.  It  is  to  delay  this  wear  that  the  bottoms  of  the  wooden 
ones  are  frequently  ti[)ped  with  brass  angle  pieces,  as  in  Fig.  317. 

The  evil  of  wear  is  a  serious  one  in  levels,  so  that  after  a 
moderate  amount  of  service,  it  becomes  necessary  to  turn  the 
level  end  for  end,  to  correct  and  average  the  observations.  The 


ifiini»juiuiiu|iiiitiiii|iiiiullnilllllllljlllllllU|lllllllli|MiiMnillllliiIlX 


*0  to 


Fig.  316. 


T 


244 


TOOLS. 


stock  being  so  short,  hastens  the  wear.  For  this  reason  levels  are 
sometimes  screwed  on  'the  toj)  of  a  long  parallel  strip,  with  the 
ends  chamfered  off  (Fig.  318).  A  usual  practice  also  is  to  lay  the 
level  on  the  top  edge  of  a  long  parallel  straight-edge,  but  this  is 


Fig.  317. 


done  in  order  to  average  the  inequalities  of  large  surfaces  which 
are  not  perfectly  true. 

Another  point  is  that  in  levels,  generally,  one  must  be  in  a 


Fig.  318. 

position  to  look  down  upon  them  in  order  to  see  the  bubble.  To 
avoid  this,  is  the  reason  why  what  are  termed,  side  views  are 
provided  in  some  levels,  so  that  the  bubble  can  be  seen  with  the 

Fig.  319. 

eyes  at  the  same  height,  or  even  a  little  below  the  level,  as  in 
Fig.  319. 

In  one  form  of  level,  instead  of  having  a  side  sight  to  the  glass 
in  the  top  of  the  instrument,  a  separate  glass  is  inserted  in  the 
body  of  the  stock,  and  protected  by  brass  discs. 


245 


STRAIGHT-EDGES  AND  SQUARES. 

Levels  for  the  use  of  machinists  should  preferably  be  of  metal. 
A  useful  kind  is  that  in  which  the  glass  tube  is  enclosed  in  a  tube' 


Fig.  320. 


Fig.  321. 


of  brass  (Fig.  319).  The  tube  protects  the  glass,  and  the  foot 
does  not  wear  sensibly  for  a  long  period.  Another  suitable  form 
for  machinists  is  made  after  the  girder 
section,  with  top  and  bottom  flanges  con¬ 
nected  with  ends,  and  connecting  curves 
or  bars,  in  place  of  a  solid  web.  These, 
having  two  flanges,  are  readily  used  as 
plumb  levels,  and  they  generally  have 
two  tubes  for  plumbing,  one  near  each 
end.  Either  flanged  face,  and  either  end, 
can  then  be  used. 

Many  levels  have  a  longitudinal  vee 
groove  along  the  base,  which  allows  them 
to  be  used  on  round  shafts,  or  tubes, 

without  affecting  their  utility  for  flat  surfaces. 

These  levels  are  rigid,  that  is,  they  have  no  means  of 
adjustment  for  the  tube  to  compensate  for  wear.  An¬ 
other  class  made  by  Starrett’s  (Fig.  320),  have  such 
means  of  adjustment.  The  ends  of  the  brass  tube  are 
prolonged  into  flat  lugs,  which  fit  over  a  couple  of  screws 
let  into  the  main  base.  A  nut  above,  and  one  below 
provide  a  means  of  raising  or  lowering  each  end  of  the 
tube,  and  locking  the  same  rigidly.  The  tube  casing  also 
can  be  turned  round  to  protect  the  glass  when  not  in 

V  use,  being  knurled  for  the  fingers. 

_  ^21  shows  a  combination  form  of  head,  fitting 

on  a  splined  rule  (of  the  type  in  Fig.  302),  which  coin- 
prises  a  spirit  level,  a  square,  and  a  bevel,  having  an  angle  of  45  . 

The  plumb  bob  is  allied  to  the  levels,  inasmuch  as  it  deter¬ 
mines  the  vertical  truth  of  objects.  Used  as  a  bob  simply. 


246 


TOOLS. 


suspended  from  a  thin  cord,  it  determines  the  perpendicular 
relations  of  centres.  When  employed  against  a  face  desired  to  be 
vertical,  it  is  combined  with  a  parallel  straight-edge,  the  bob  being 
contained  in  a  hole  cut  through  the  straight-edge  near  the  bottom. 
It  is  then  termed  a  plumb  rule.  The  general  objection  to  the 
common  plumb,  of  brass  or  lead,  is  that  it  sways  a  long  time 
before  coming  to  rest,  which  is  the  reason  why  the 
workman  steadies  it  with  his  fingers.  To  avoid  this 
trouble  the  bob  shown  in  Fig.  322,  is  designed.  It 
is  a  long  hollow  rod,  small  in  proportion  to  length, 
and  is  filled  with  mercury,  which  makes  it  unusually 
heavy.  The  small  diameter  allows  it  to  be  used  close 
to  walls,  and  upright  faces.  A  silk  line  is  attached 
to  the  top  cap,  for  suspension. 

A  useful  tool  is  shown  in  Fig.  323,  employed  in  connection 
with  ratchet  drills,  on  cylindrical  surfaces,  as  those  of  boilers. 
The  tool,  made  of  sheet  metal,  is  stood  upright  on  the  work,  and 
when  the  centre  of  the  drill,  or  the  ratchet  body  coincides  with 
the  point  of  the  instrument,  it  is  square  with  the  job. 


CHAPTER  XXL 

Surface  Gauges,  or  Scribing  Blocks. 


The  Work  of  Lining-out— Preliminary  Checking  of  Leading  Dimensions 
Centre  Lines— Cardinal  Dimensions— The  Basis  of  a  Level  Table— Pack¬ 
ing  up-Details-Scribing  Block-Its  Work-IllustraUons  of  its  Use- 
Differences  between  Good  and  Bad  Forms— Various  Kinds— Refinements 
Described —  Scribers. 


rHE  general  problem  in  the  work  of  lining-out  is  that  of 
scribing  any  lines  on  surfaces  in  any  position,  and  also  of 
ensuring  absolute  relations  between  lines  on  the  same, 
or  on  different  surfaces,  for  which  there  is  often  no  means  of 
direct  checking,  as  there  is,  for  example,  on  a  level  plane,  or  on 
a  drawing.  Besides  this,  the  truth,  approximate  or  exact— always 
using  the  words  in  their  shop  sense-of  horizontal,  or  vertical 

faces  is  often  included.  , 

A  large  section  of  engineers’  work — the  largest  m  the  average 

shop— is  done  by  lining  out,  and  working  by  these  lines.  All 
massive  work  is  so  treated,  and  all  that  of  medium  dimensions  in 
which  the  quantity  turned  out  is  not  sufficient  to  pay  for  templets, 
iigs  and  gauges.  It  is  one  of  the  most  important  sections  of 
practice.  Usually  the  men  who  do  it — ^the  markers-out  perform 
no  other  duties,  though  in  numerous  instances  a  man  has  to  line 
out  his  own  work,  and  then  machine,  and  fit  it  up.  The  tendency, 
however,  for  many  years  has  been  to  throw  this  particular  depart¬ 
ment  more  and  more  into  the  hands  of  the  marker-out,  who 
thereby  acquires  deftness  and  experience  which  shorten  the 

Ae  work  of  lining  off  we  meet  with  a  very  different  set  of 
conditions  from  those  which  exist  in  working  by  gauge.  T  e 
difference  is  that  between  laying  out  dimensions  to  be  worked  by, 
and  in  checking  dimensions  already  tooled.  But  after  work  is 
lined  out  and  tooled,  gauges  are  often  employed  to  check  it 
by,  or  the  rule  and  calipers  may  be  used  for  the  purpose,  so 


248 


TOOLS. 


that  there  is  an  overlapping  of  these  broad  methods.  Again,  the 
templet  is  a  half-way  device,  used  instead  of  lining  out,  or  as 
supplementary  thereto,  to  save  the  trouble  of  marking  out  a 
number  of  lines  with  rule  and  compass,  &c. 

In  almost  all  cases  we  may  say  that  in  practice  the  lines 
marked  out  are  never  worked  by,  in  the  sense  of  trusting  to  them 
absolutely  without  further  check,  in  any  but  the  roughest  produc¬ 
tions.  The  turner  and  machinist  check  results  with  movable 
calipers,  and  refer  these  to  the  rule ;  or  measure  with  the  rule 
direct,  thus  coming  back  to  rule  measurement  as  the  last  check 
on  work  previously  marked  by  it.  This  represents  common,  or 
average  practice  now.  Gauges  and  templets  are  also  made  from 
the  rule,  and  used  to  check  the  results  of  tooling ;  but  these  again 
in  the  general  system  depend  for  their  accuracy  on  the  rule,  and 
the  ideas  of  the  workman  with  regard  to  the  limits  of  accuracy 
necessary  or  permissible,  working  as  exact  as  vision  is  able  to 
detect,  or  full,  or  bare,  as  seems  necessary  for  tight,  and  easy  fits. 

The  instruments  of  measurement  used  for  lining-out  are  rules, 
compasses,  dividers  and  trammels,  scribers,  scribing  blocks,  or 
surface  gauges,  and  calipers ;  assisted  by  squares,  protractors, 
straight-edges,  and  centre  punches. 

Before  the  marker-out  can  set  out  all  the  lines  by  which 
machining  is  to  be  done,  it  is  necessary  to  check  leading  dimen¬ 
sions  roughly.  The  reason  for  this  is,  the  inaccuracy  present  in 
cast,  and  forged  work,  which  has  to  be  averaged  by  a  give-and- 
take  process,  by  allowing  more  in  some  parts,  and  less  in  others 
for  tooling  than  the  regular  amount.  This  is  not  very  easy  to  do 
where  allowances  are  cut  fine  on  intricate  work.  Several  centres, 
and  over-all  distances  may  then  have  to  be  checked,  as  well  as 
the  relations  of  faces  or  the  axes  of  holes.  Hand-made  forgings 
and  jobbing  castings  of  large  dimensions  are  the  most  awkward 
to  average,  while  drop  forgings  and  plate-moulded  castings  are  the 
least  inaccurate.  In  fact,  in  these  the  work  of  lining-out  is  gener¬ 
ally  saved,  and  templets  substituted,  because  the  forgings  and 
castings  show  practically  no  differences  in  dimensions. 

In  the  cylinder,  Fig.  324,  the  dimensions  which  have  to  be 
mutually  checked  are  seven  in  number.  There  are  the  foot  a, 
flange  b,  facing  c,  and  flange  d,  which  have  to  stand  either  square 
with  each  other  or  parallel.  But  when  these  are  averaged  right, 
the  bore  E  may  be  found  too  much  to  one  side  or  another,  making 


SURFACE  GAUGES. 


249 


the  distance  a  or  d  from  the  centre  incorrect.  Or  the  flanges  f, 

F  may  be  out  of  square  with  the  bore,  and  with  the  foot  a,  or  flange 
B.  The  question  is  far  less  often  that  of  whether  any  single  sec¬ 
tion  will  hold  up  to  size,  as  whether  all  will  hold  up,  when  standing 
in  their  proper  relations,  square,  or  it  may  be  at  a  bevel,  and  to 
correct  centres.  Hence  the  reason  why  careful  averaging  by  the 
liner-out  is  necessary.  It  may 
be  thought  that  the  remedy  for 
this  would  be  to  give  plenty  of 
allowance  for  tooling.  There 
are  limits,  however,  to  this, 
though  it  is  done  to  a  reason¬ 
able  extent.  It  is  obvious  that 
the  finer  allowances  are  cut  for 
machining,  the  greater  is  the  care 
which  has  to  be  exercised  in  the 
production  of  pieces,  whether 
castings  or  forgings,  of  reason¬ 
ably  uniform  shape  and  dimen¬ 
sions. 

Or,  taking  the  common  illus¬ 
tration  in  Fig.  325,  such  a 
forging  when  made  on  the  anvil 
is  very  unlikely  to  be  even 
approximately  exact.  To  set  it 
out,  the  marker-off  has  to  start 
from  centre  lines  a,  d,  ran  round 
on  each  face,  the  planes  of  which 
would  cut  each  other  at  exact 
right  angles.  Then  lines  for  the 
three  boss  centres  have  to  be 
squared  up  on  all  faces.  Pro¬ 
bably  the  boss  centres  will  not 

come  as  they  should,  and  two  or  three  attempts  may  have 
to  be  made  to  locate  such  centres  as  will  permit  of  each  boss 
tooling  up  to  its  proper  diameter.  The  faces  of  the  end  bosses 
may  not  measure  alike  from  the  faces  of  the  central  boss,  and 
then  the  centre  line  d  may  have  to  be  shifted  to  average  these. 
Or  the  forging  may  even  have  to  be  set  afresh  by  the  smith. 

In  most  work  there  are  cardinal  dimensions,  and  secondary  or 


250 


TOOLS. 


less  important  ones.  The  intelligent  liner-out  goes  for  the  first 
ones,  and  takes  little  account  of  the  second.  Another  man  makes 
no  such  distinction,  but  treats  all  alike.  The  cardinal  dimensions 
in  the  foregoing  figures  are  those  that  have  been  mentioned. 
The  thickness  of  flanges  in  Fig.  324,  and  those  of  the  webs  in 


Fig.  325- 


Fig.  325,  have  to  be  accommodated  to  the  others — within  reason, 
of  course,  because  too  great  thinning  down  of  a  flange  or  web 
would  condemn  the  piece  as  a  waster  in  a  shop  where  regard  is 
had  to  reputation. 

In  lining  off  work,  the  basis  of  operations  is  the  face  of  the  iron 
marking-off  table,  the  face  and  edges  of  which  are  planed  truly  and 

square.  From  its  face  the  surface  gauges 
are  worked,  and  squares  are  set  up.  The 
first  thing  to  do,  therefore,  is  to  fix  up 
the  casting  or  forging  on  the  table  in  such 
a  way  that  it  cannot  rock,  and  in  such  a 
position  that  the  first  set  or  sets  of  lines 
can  be  scribed  or  squared  from  the  table. 
Frequently,  when  a  suitable  face  exists,  a 
cut  is  taken  over  that  face  first,  and  by 
that  the  work  is  laid  upon  the  table.  Such  would  often  be  done 
with  the  face  A  in  Fig.  324,  though  a  rough  preliminary  checking 
over  of  the  casting  would  be  desirable.  If  the  face  is  utilised  in  the 
rough,  as  in  Fig.  324,  it  has  to  be  packed  up  on  wedges,  as  shown, 
or  on  blocks  as  in  Fig.  325,  until  an  average  level  is  obtained,  and 
the  face  to  be  tooled  is  scribed  round.  Sets  of  parallel  blocks  of 


SURFACE  GAUGES. 


251 


various  thicknesses  are  part  of  the  equipment  of  the  marking-off 
table,  being  solid  blocks  planed  on  all  faces,  or  I  sections. 
Wedge  blocks  (Fig.  326)  are  also  used. 

For  circular  work  the  vee  blocks  are  em¬ 
ployed,  and  these  are  fixed  (Fig.  327)) 
adjustable  for  height  (Fig.  328),  or  one 
block  contains  several  vees  as  in  Fig.  329- 
By  these  devices  artificial  bases  are  ob¬ 
tained  for  pieces  of  work  of  all  shapes 
above  the  level  of  the  table,  whence  the 

scribing  blocks,  squares,  and  other  instru¬ 
ments  of  measurement  and  checking  are 
used. 

An  important  point  is  that  all  the  lining- 
out  possible  should  be  done  at  one  setting, 
to  save  time,  and  to  get  on  all  the  lines 
available  before  changing  the  position  of  the 
work  on  the  table,  a  precaution  which  con¬ 
duces  to  accuracy.  Many  pieces  of  work, 
of  course,  are  lined  out  entirely  at  one 
setting. 

Every  line  struck  out  in  this  way  is  put 
on  with  a  pointed  tool  of  some  kind 
scriber,  compass,  &c., — and  is  therefore 
liable  to  error.  And  every  dimension  is 
taken  from  a  rule,  and  is  liable  to  error  in 
the  transference.  To  lessen  risk  of  the  first, 
the  lines  are  drawn  very  fine,  on  a  surface 
whitened  with  chalk,  or  with  a  wash  of 


Fig.  328. 


whitening.  As  these  lines  would  easily 
become  obliterated  in  subsequent  handling 
and  in  contact  with  the  oil  about  the 
machines,  their  course  is  indicated  with 
fine  centre  punch  pops  (Figs.  324  and  325). 

Frequently,  too,  in  turned  and  bored  work  a 
second  line  is  struck  concentric  with  the 

working  line,  to  remain  as  a  “witness”  after 

the  work  is  machined  that  it  has  been  tooled  truly,  as  m  Fig.  324. 

Though  the  scribing  block  is  mainly  a  marking  instrument, 
yet  it  is,  as  its  synonym  implies,  a  “  surface  ’  gauge.  Its  turned- 


252 


TOOLS. 


down  point  is  employed  in  checking  or  testing  the  truth  of  a 
horizontal  surface  by  contact  therewith,  the  sense  of  touch 
coming  into  play.  This  is  an  extremely  handy  means  of  levelling 
up,  in  place  of  a  direct  measurement  by  the  rule,  besides  which 
there  are  numerous  instances  in  which  the  latter  would  not  be 
available,  as  in  circular  work,  the  highest  surface  of  which  would 
not  be  accessible  by  the  rule.  The  straight  point  both  marks 
and  checks  lines  on  vertical  or  sloping  faces.  The  means  of 
effecting  minute  adjustments  for  height  are  sometimes  simple 
and  crude,  in  others  very  fine  and  precise.  In  most  the  pillar  is 
fixed  in  a  base ;  in  some  it  is  hinged.  The  base  must  be  massive, 
in  order  to  ensure  the  steadiness  of  the  gauge.  Its  bottom  must 
be  true :  it  is  generally  hollowed  out  underneath  to  bear  around 
annular  edges  only.  The  fittings  of  the  scriber  and  its  block 


must  be  very  good.  Some  gauges  are  made  for  sliding  on  a  level 
surface  only,  others  are  vee’d,  and  others  are  vee’d  both  on  the 
end  and  bottom,  to  be  used  either  way. 

The  work  of  the  scribing  block  is  of  a  manifold  character, 
both  in  regard  to  the  actual  work  of  marking  out  and  as  a  preli¬ 
minary  thereto.  Say  we  want  to  level  a  casting  or  forging  before 
lining  it  out  for  tooling  (Fig.  330).  The  instrument  is  then  used 
as  a  surface  gauge  first,  the  turned-down  point  indicating  the 
position  of  the  face  in  relation  to  the  face  of  the  table,  whence 
the  lines  are  to  be  scribed  presently.  Blocking  and  wedges  afford 
the  means  whereby  the  casting  is  levelled  up  to  the  required 
position  indicated  by  the  gauge. 

This,  in  passing,  is  a  different  thing  from  using  a  spirit  level, 
although  levelling  is  the  object  in  view  in  both  cases.  But  using 


SURFACE  GAUGES. 


253 


a  gauge,  the  basis,  whether  the  marking-off  table  or  machine  bed, 
need  not  be  perfectly  horizontal,  while  with  a  spirit  level  it  must 
be.  Hence  the  surface  gauge  is  often  a  very  much  more  con¬ 
venient  tool  to  employ  than  the  spirit  level. 

The  surface  gauge  reversed  is  used  for  the  levelling  of  bottom 
faces.  Suppose  that  the  tooling  of  a  piece  of  work  has  to  be 


done  in  relation  to  a  face  already  tooled,  or  in  any  case  taken  as 
one  to  commence  from,  and  that  face  cannot  be  laid  directly  upon 
the  table  because  a  boss  or  lug  or  other  projection  comes  in  the 
way :  then  the  piece  of  work,  suitably  packed  up,  is  levelled  by 
bringing  the  turned-up  point  of  the  scriber  against  the  bottom 
face  (Fig.  331),  and  so  making  corrective  adjustments. 

The  scribing  block  is  employed  largely  for  transferring  dimen- 


Fig-  332- 

sions,  as  well  as  for  marking  centre  lines  and  edge  lines.  When 
the  vertical  face  of  a  piece  of  work  is  a  plane,  it  is  easy,  of  course, 
to  lay  off  dimensions  one  above  another  directly  with  compasses  or 
dividers  (Fig.  332).  But  when  the  faces  to  be  marked  stand  out 
at  different  levels,  this  is  not  practicable.  Of  course  it  can  be 
done  after  a  fashion  by  using  a  compass  or  trammel  with  an  exten 
sion  leg,  but  that  is  not  accurate  enough.  The  proper  course. 


254 


TOOLS. 


Fig-  333- 


then,  is  to  set  out  the  dimensions  on  a  block  (Fig.  333,  a),  stand 
that  upright,  and  transfer  the  lines  directly  from  that  to  the  faces 

of  the  work.  Or  the  rule  is  stood 
on  end  against  a  square  block  to 
keep  it  upright,  and  so  used. 
Several  firms  now  make  height¬ 
measuring  appliances  specially  for 
the  marking-off  table  for  this 
particular  purpose.  In  one  form 
a  divided  stem  is  fixed  permanently 
in  a  circular  base;  in  another  a 
common  steel  rule  is  clamped  in 
a  vertical  position  on  a  base  (Fig. 

334)- 

Another  use  of  the  scribing  block  is  the  locating  of  centres 
of  circular  work,  either  shafts  or  discs.  The  first  is  rotated  in 
vee  blocks  ;  the  latter  on  edge  on  the  table  into  fresh  positions, 
in  each  of  which  a  short  line  is  scribed  in  a 
position  approximating  to  the  centre,  and  the 
mean  of  four  to  half-a-dozen  such  lines  taken 
as  the  centre. 

These  are  the  leading  functions  of  the 
surface  gauge  or  scribing  block,  but  many 
forms  are  designed  for  a  wider  range  of 
operations. 

The  fault  which  all  the  home-made  blocks 
have  is  not  that  they  are  badly  fitted — for  they 
are  generally  made  very  neatly  as  a  work  of 
love — but  that  they  have  no  fine  adjustments. 

When  the  pinching  screw  is  slackened,  there  is 
nothing  but  the  fingers  to  prevent  the  scriber 
from  dropping  from  its  position.  Consequently, 
when  fine  adjustments  are  being  effectedj  the 
screw  is  partly  released,  and  the  point  tapped 
with  rule,  or  scriber,  or  centre  punch,  much  as 
caliper  legs  are  tapped  with  the  same  object  in  Fig.  334. 

view.  And  this  tapping  is  a  very  uncertain  and 
clumsy  process.  The  best  manufactured  surface  gauges  have  a 
spring  friction  enclosed  in  the  boss  holding  the  scriber,  by  means 
of  which  both  the  sliding  sleeve  and  the  clamp  or  clasp  which 


L 


V 


SURFACE  GAUGES. 


255 


grips  the  scriber  are  just  retained  in  position,  though  the  screw  is 
loosened.  A  fine  adjustment  for  height  is  effected  by  a  knurled 
disc,  which  on  being  turned  slowly  revolves 
the  clasp  in  which  the  scriber  is  held,  so  that 
it  can  be  set  to  any  exact  height.  Fig.  335 
illustrates  a  Brown  &  Sharpe  gauge  of  this 
kind. 

In  another  type  (Fig.  336)  the  height  is 
adjusted  finely  by  a  lever  and  screw  attached 
to  a  socket,  into  which  the  post  is  stepped. 

The  point  of  the  screw  rests  on  the  exten¬ 
sion  of  the  base  block,  and  by  turning  it  the 
fine  adjustment  of  the  point  is  effected. 

In  a  Starrett  gauge  (Fig.  337)  the  height 
is  adjusted  micrometrically  by  a  nut  on  the 
base,  reading  to  thousandths  of  an  inch. 

An  extension  piece  is  fitted  (Fig.  338)  to 
increase  the  height  of  the  stem  by  6  in.  In 
another,  by  the  Stevens  Arms  and  Tool 
Company  (Fig.  339),  fine  adjustment  is 
effected  by  turning  a  thumb-screw  at  the 

top  of  the  post 
to  graduations, 
each  of  which 
gives  an  adjust-  Fig.  335. 

ment  of  a  thou¬ 
sandth.  The  scriber  is  used  as  a 
depth  gauge,  passing  perpendicularly 
through  the  hole  shown  in  the  base. 
The  knob  at  the  top  is  to  prevent  the 
knurled  nut  from  being  run  right  off, 
and  lost. 

Fig.  340  is  a  Starrett  surface 
gauge  in  which  the  base  is  cut  away 
in  one  part  to  permit  of  the  use  of 
the  tool  as  a  depth  gauge.  Fine 
336-  adjustment  is  effected  by  the  knurled 

nut  in  the  base.  There  is  also  a 
spiral  spring  in  the  base  to  take  up  backlash. 

Among  other  refinements,  the  Billings  gauge  (Fig.  341)  should 


256 


TOOLS. 


Fig-  338- 


SURFACE  GAUGES. 


257 


be  mentioned,  in  which  the  scriber  is  steadied  by  two  blocks  or 
lugs— the  one  in  which  it  is  carried  and  to  which  it  is  clamped, 
and  another  higher  up  connected  to  it  with  a  screw,  and  sliding 
on  the  post  or  standard.  The  upper  one  is  clamped  to  the  post. 
In  another  surface  gauge  a 


0 


Q 


spirit  level  is  fitted  in  the 
base  to  test  a  surface  by. 

Fig.  342  represents  a 
gauge  by  the  Massachusetts 
Tool  Company,  in  which 
fine  adjustment  is  by  the 
milled-headed  screw  in  the 
base,  while  the  spring  below 
takes  up  backlash.  The 
front  end  of  the  base  is  cut 
away  at  the  centre  to  permit 
the  use  of  the  scriber  as  a 
depth  gauge.  These  are 
nice  refinements  which  are 
not  present  in  the  shop- 
made  articles. 

Many  gauges  are  made 
with  a  vee’d  base  to  permit 
them  to  be  slid  along  shafts  and  bars  for  the  lining-out  of  work  on 
those  shafts,  which  would  otherwise  be  inaccessible.  These  occur 
in  home-made,  and  in  manufactured  forms,  but  the  latter  are  gene- 


ns 


-O. 


Fig.  342. 


Fig.  343- 


rally  found  in  combination  types  used  for  flat  and  circular  surfaces. 
Fig.  343  shows  the  home-made  article.  But  more  handy  dwarf 
scribing  blocks  are  manufactured,  provided  with  a  vee  on  the 
bottom  face  or  on  the  end,  to  permit  them  to  be  used  on  circular 

R 


TOOLS. 


258 

rods,  shafts,  or  boring  bars.  In  one  form,  hardened  pins  stand 
out  from  one  face  to  allow  the  gauge  to  be  slid  along  a  straight  or 
curved  edge,  or  in  a  groove  such  as  those  on  planing  and  milling 
machine  tables,  &c. 

Manufactured  surface  gauges  may  be  divided  into  two  very 
broad  types,  the  common  forms  just  noticed,  and  the  universal. 
The  latter  are  comparatively  recent.  Their  broad  features, 
modified  by  different  manufacturers,  are  these,  Fig.  344,  repre¬ 
senting  a  typical  Brown  &  Sharpe  form  : — 

The  gauge  is  supported  and  hinged  at  one  end  of  a  rather 
heavy  rectangular  base.  The  post  fits  into  a  boss  which  swivels 


in  a  vertical  plane  in  a  lug  standing  up  on  the  base,  so  that  it,  with 
its  scriber,  can  be  set  in  any  position  from  vertical  to  horizontal. 
This  permits  the  use  of  the  scriber  in  any  position,  even  below 
the  base,  for  marking  lines  or  gauging  a  depth.  The  post  with 
the  scriber  is  held  in  any  position  by  friction  springs  during  the 
making  of  exact  adjustments,  when  the  clamping  nut  is  loosened, 
and  remains  so  until  the  adjustments  are  effected,  when  a  slight 
turn  of  the  nut  secures  the  parts  in  the  required  position. 

To  render  these  instruments  still  further  adaptable,  the  base  is 
frequently  grooved  to  fit  circular  work.  One  end  of  the  block  as 
well  is  also  often  grooved  similarly  to  extend  the  range  of  its 


SURFACE  GAUGES. 


259 


utility.  Another  improvement  sometimes  included  is  the  fitting, 
just  now  alluded  to,  of  two  pins  through  the  block  near  the  rear 
of  the  base,  as  in  some  of  the  Starrett  tools.  When  these  are 
pushed  down,  the  base  can  be  slid  along  the  edge  of  a  surface 
plate,  or  the  edge  of  a  slot  in  the  bed  of  a  planing  machine  when 
straight  or  parallel  lines  have  to  be  marked  on  the  horizontal 
surface  of  a  piece  of  woik. 

A  good  many  operations  can  be  performed  with  a  surface 
gauge  of  this  kind  that  are  beyond  the  range  of  the  rigid  pillar 
type  with  an  ungrooved  base.  The  pins  permit  it  to  be  slid  along 
straight  edges  for  marking  parallel  lines  on  horizontal  faces,  or 
round  curved  edges  for  concentric  curves.  A  grooving  at  the 
front  edge  allows  the  post  to  be 
passed  down  through  that  groove, 
so  that  the  scriber  will  mark  lines 
parallel  with  the  base.  Lines 
can  be  marked  round  cylindrical 
work,  while  the  bottom  groove 
rests  on  a  central  shaft  or 
mandrel.  Lines  can  be  marked 
on  wheels,  discs,  and  circular 
work,  the  centre  of  which  is 
inaccessible  by  reason  of  the  pre¬ 
sence  of  shafts  and  spindles,  the 
gauge  being  set  around  these. 

In  one  universal  instrument — the 
“Carr” — the  base  has  two  horns 
standing  up  at  a  right  angle,  so 

permitting  the  block  to  be  slid  along  a  true  edge,  and  fulfilling 
the  function  of  the  pins  just  noted.  The  post  is  pivoted  to  fall 
between  these  lugs  when  required  to  work  in  a  horizontal  position. 
It  can  also  be  turned  down  to  be  used  underneath  a  piece  of  work 
or  along  a  bottom  edge.  There  is  a  vee  milled  on  one  side  of 
the  upper  surface  which  permits  the  instrument  to  be  used  around 
the  edge  of  a  face-plate,  or  on  the  end  of  a  shaft.  This  gauge  has 
a  fine  adjustment  of  ^  to  |  in.  for  the  point  of  the  scriber, 
operated  by  an  eccentric  washer  at  the  base  of  the  post. 

In  another  gauge  the  post  is  enclosed  in  the  middle  of  a 
block,  in  which  it  is  permitted  a  movement  of  three-fourths  of  a 
circle.  A  large  vee  groove  at  one  end  permits  the  instrument 


26o 


TOOLS. 


to  be  used  round  the  edges  of  curved  work,  either  face  or  cylin¬ 
drical.  A  tongue  on  one  side  allows  the  gauge  to  be  slid  along 
the  edges,  or  in  the  grooves  of  planer -tables,  I'tc.  In  another 
universal  gauge  a  still  further  range  is  included— that  of  trammel 
points.  There  is  another  very  useful  combination  tool,  the 
Stafford  &  Whipple  planer  and  surface  gauge  (Fig.  345),  designed 
specially  for  use  on  the  planer.  A  diagonal  rule  on  a  broad  base 
carries  an  adjustable  sliding  block,  which  holds  the  scriber  point, 
aud  a  horizontal  test  foot.  The  latter  is  employed  for  measuring 
the  height  of  the  tool  point  from  the  planer  table.  The  gradua¬ 
tions  on  the  inclined  rule  are  such  that  the  readings  give  the 


exact  vertical  height  in  sixteenths.  The  foot  is  clamped  with  one 
knurled  screw,  the  scriber  with  another. 

A  form  of  scribing  block  is  shown  in  Fig.  346,  with  a  rigid 
scriber  which  cannot  be  swivelled,  but  it  lacks  some  of  the 
advantages  of  the  latter  type.  It  is  handy,  however,  for 
making  horizontal  lines  at  various  heights,  and  may  therefore 
usefully  supplement  the  gauges  which  have  a  wider  range  of 
adaptability. 

The  last  illustration  of  a  surface  gauge  is  one  of  the  micro¬ 
meter  type  (Fig.  347).  The  principles  embodied  in  micrometric 
instruments  are  explained  on  pp.  288,  291,  so  nothing  will  be  said 
about  them  here.  The  instrument  illustrated  combines  this  fine 
method  of  measurement  with  the  utility  of  the  surface  gauge.  In 


SURFACE  GAUGES. 


261 


addition  to  these,  large  measurements  in  inches  are  provided 
for  by  the  fitting  of  end  measuring  plugs  of  standard  lengths. 

In  Fig,  347  the  stem  a  of  the  gauge  is  hollow,  and  receives 
the  plugs  seen  in  the  broken  sections,  measuring  i,  2,  and  3  in. 
long  respectively,  and  which  can  be  used  separately,  or  in  com¬ 
binations,  giving  a  maximum  range  of 
6  in.  in  height.  The  lowest  plug  rests 
on  a  hardened  adjustable  stud  in  a 
recess  in  the  foot,  by  which  any  possible 
wear  can  be  taken  up.  The  upper  end 
of  the  plug  in  use  receives  an  abutment 
piece  formed  on  the  inner  end  of  the 
arm  b.  These  plugs  give  dimensions 
in  even  inches  from  i  to  6  in. 

Dimensions  between  these  are  ob¬ 
tained  by  the  micrometer  c  on  the 
outer  end  of  the  arm  b,  which  has  a 
range  of  i  in ,  reading  to  one-half 
thousandths,  the  end  of  the  plunger 
D  bearing  on  the  surface  of  the  work. 

In  these  numerous  'designs  of 
surface  gauges  or  scribing  blocks  we 
have  wandered  far  away  from  the 
simple  instruments  which  the  appren¬ 
tice  makes.  They  have  developed  from  the  plain  gauge  into 
very  fine  instruments  of  precision,  capable  of  extremely  fine 
adjustments,  which  are  not  only  relative,  but  readable  in 
absolute  measurements.  We  shall  also  observe  similar  refine¬ 
ments  in  other  classes  of  tools  of  common  types.  The  utilities 


Fig.  348. 


of  the  gauge  are  therefore  much  enhanced,  rendering  it  suitable 
to  the  higher  demands  which  are  now  made  upon  the  marker-out 
and  the  machinist  than  formerly. 

The  common  scriber  of  the  shops  is  usually  made  from  a  bit 
of  steel  rod,  one  end  of  which  is  bent  round  for  marking  upwards 
on  surfaces  that  face  downwards,  and  in  awkward  recesses,  &c. 


262 


TOOLS. 


The  central  portion  is  either  left  smooth,  or  is  twisted  to  afford  a 
grip  for  the  hand.  Better  instruments  are  manufactured  by  the 
insertion  of  the  pointed  portions  into  a  central  stock  which  is 
considerably  larger  than  the  body  of  the  wire  and  knurled  as  in 
Fig.  348.  The  thicker  ends  of  the  points  are  also  knurled 
similarly.  The  stock  is  shown  in  section  in  Fig.  349. 

These  instruments  are  used  without  any  extraneous  aid,  save 
the  guidance  afforded  by  a  straight-edge,  or  an  edge  having  an 
outline  corresponding  with  that  of  the  piece  which  is  marked 
from  directly.  The  patternmaker  uses  a  knife  edge  for  scribing, 
but  the  machinist  scribes  with  points  only.  The  tool  must  be 
properly  tempered  to  retain  its  keenness  of  point,  and  must  be 

held  at  a  very  slight  angle  only 
with  the  edge  from  which  the 
marking  is  done.  In  this  way 
very  fine  lines  can  be  marked 
accurately  for  centre  popping 
and  working  by. 

The  scriber,  or  striking  knife  is  used  by  woodworkers  for 
marking  lines  on  timber  as  guides  for  planing,  cutting  by  the 
edge  of  a  straight-edge,  or  of  a  templet  in  some  cases,  which 
becomes  the  guide  to  the  knife.  It  is  double  ended,  one  end 
cutting  in  like  a  chisel,  or  a  gauge  point,  the  other  scratching 
only.  Bent  scribers  are  used  for  marking  in  places  that  cannot 
be  reached  by  a  straight  tool. 


CHAPTER  XXII. 


Compasses  and  Dividers. 

Distinction  between  Coarse  and  Fine  Adjustment — Stiffness  of  Legs — Modified 
Forms — Combination  Types — Trammels — Examples — Centring  Balls — 
Parallel  Dividers. 

The  varied  forms  of  compasses,  dividers,  and  trammels  will 
now  be  considered.  Many  of  these  bear  strong  resem¬ 
blances  to  some  forms  of  calipers,  similar  devices  being 
employed  in  each  for  the  purpose  of  effecting  precise  adjustments. 
The  term  divider  is  usually  applied  to  those  instruments  which 
have  spring  heads,  and  compass  to  those  which  are  hinged  or 
pivoted.  The  first  named  are  not  quite  so  rigid  as  the  latter,  to 
which  additional  stiffness  is  afforded  by  the  quadrant  and  wing 
nut.  But  the  first  are  properly  kept  for  small  radii  and  fine 
precision  work,  the  latter  for  larger  radii  and  deeper  lines,  or  on 
rougher  surfaces.  But  the  two  types  overlap  constantly.  For 
pitching  out,  or  general  dividing  out,  the  screw  fitted  to  a  divider 
is  better  than  the  quadrant  and  wing  nut.  But  the  latter  are 
often  supplemented  by  a  fine  adjustment  screw  similarly  to  the 
calipers  of  that  design.  To  work  to  close  dimensions  with  any 
instruments  having  adjustable  legs  renders  a  means  of  fine 
adjustment  indispensable,  and  therefore  there  are  few  high-class 
tools  now  made  without  that  provision.  Varied  widely  though 
these  are,  the  beam  compasses  or  trammels  are  equally  so,  having 
their  coarse  and  fine  adjustments,  and  lengthening  points  in  many 
designs.  For  curves  above  a  few  inches  in  radius  the  trammels 
are  essential,  if  for  no  other  reason  than  to  have  the  legs  per¬ 
pendicular  to  the  surface  of  the  work.  And  there  is  no  limit  save 
the  rigidity  of  the  beam  to  the  radius  of  the  curve  which  they  will 
strike.  All  high-class  instruments  of  the  kinds  here  enumerated 
have  both  coarse  and  fine  adjustments — coarse  with  thumb-screws, 
and  fine  with  an  independent  screw  of  fine  pitch.  Some,  like 


264 


TOOLS. 


the  spring  dividers,  contain  practically  only  the  fine  adjustment 
by  the  wing  nut,  a  rapid  movement  for  approximate  adjustment 
of  the  points  being  accomplished  by  pulling  the  legs  towards  each 
other  to  release  the  friction  next  the  screw,  and  then  by  running 
the  latter  along  by  the  finger  until  the  spacing 
of  the  legs  is  roughly  that  required. 

A  most  important  point  in  the  design  of 
all  compasses  and  dividers  is  stiffness  of  legs. 
This  is  quite  consistent  with  lightness.  Flimsy 
legs  inevitably  spring,  and  alter  the  truth  of  a 
circle,  large  or  small,  even  during  the  act  of 
describing  it,  and  they  chatter  in  the  act  of 
scribing.  If  used  for  setting  out  points  of 
equal  division,  they  will  not  mark  equally,  but 
give  variable  centres  according  to  the  degree 
of  pressure  exercised  upon  them,  and  the  way 
in  which  they  are  grasped. 

When  taking  dimensions  from  a  rule  with 
compasses  or  dividers,  they  are  never  started 
from  the  end,  but  in  one  of  the  divisions, 
usually  the  first  from  the  end,  which  is  more 
accurate  than  attempting  to  work  from  the 
end. 

A  good  many  dividers  have  a  milled  head  standing  up  beyond 
the  spring  for  the  purpose  of  rotating  them  when  striking  circles. 
These  resemble  the  ends  of  a  draughtsman’s  small  ink,  pencil,  and 
point  compasses,  and  are  more  favourable  to  the  rotation  of  the 


Fis-  352. 


instrument  than  the  handling  of  the  spring  itself,  more  especially 
in  the  case  of  small  circles.  Fig.  350  illustrates  a  pair  of  this  type. 

Instead  of  a  solid  nut  of  the  wing  or  milled  type,  the  devices 
shown  in  Figs.  351  and  352  are  sometimes  used.  The  legs  being 


COA^FASSES  AND  DIVIDERS. 


265 


pulled  together  by  the  fingers  to  relieve  the  nut  of  pressure,  the 
latter  is  then  readily  disengaged  from  and  slipped  over  the  threads 
of  the  adjusting  screw,  until  the  approximate  position  of  the  legs  is 
reached,  when  the  nut  is  again  allowed  to  resume  its  normal 
position  of  engagement  with  the  screw  for  the  purpose  of  making 
precise  adjustments.  The  pressure  of  the  legs  on  the  nose  of  the 
nut  causes  the  latter  to  grip  the  thread.  This  neat  device  saves 
much  time  and  delays  the  wear  of  the  thread  in  the  nut,  which  is 
always  a  vulnerable  point.  Another  type  of  this  device  takes  the 
form  of  a  spring  chuck  formed  with  the  adjusting  nut,  pressure  on 


the  nose  of  which  closes  the  jaws  in  on  the  screw,  but  when  the 
pressure  is  released  they  spring  out  naturally. 

A  modification  of  the  compass  consists  in  making  the  marking 
points  distinct  from  the  legs,  and  fitting  them  in  grips  (Fig.  353), 
instead  of  socketing  the  legs,  as  is  often  done.  The  advantages 
are  that  whatever  the  spread  of  the  legs,  the  points  can  always  be 
kept  perpendicular  to  the  surface  of  the  work,  thus  avoiding  all 
tendency  to  be  forced  outwards  by  the  pressure  of  the  hand.  The 
same  legs  being  curved  at  the  opposite  end,  serve  as  calipers. 
Also,  the  legs  being  slid  up  or  down  in  their  grips  can  be  used 
to  strike  curves  on  levels  above  or  below  that  of  the  centre,  as 
in  Fig.  354.  Further,  the  legs  being  straightened  out  into  line. 


266 


TOOLS. 


serve  as  trammel  points,  Fig.  355 — moderate  range  of  radii  then 
being  obtainable  by  bending  the  legs  at  different  angles.  The 
same  instrument  is  shown  in  Fig.  356  with  another  pair  of  legs, 
which  are  used  as  compasses  or  as  external  calipers.  Fig.  353 
illustrating  internal  calipers. 


Fig-  355- 


Though  combination  tools  are  not  as  a  rule  desirable,  yet 
there  are  many  exceptions.  Men  who  have  to  work  on  out-of- 
door  jobs  know  their  advantages  in  saving  dead  load  to  be  carried, 
and  in  not  having  to  be  bothered  with  a  lot  of  tools  scattered 

about.  Besides  the  tool  just  de¬ 
scribed,  a  few  examples  are  the 
following : — 

A  pair  of  compasses  with  a 
hinged  joint  and  quadrant  wing 
with  fine  adjusting  screw  has  its 
legs  formed  as  sockets.  Into 
these,  two  pairs  of  points,  long 
and  short,  fit,  also  a  pair  of  bent 
caliper  legs,  the  curves  of  which 
may  be  turned  inside  or  out  to 
suit  either  form  of  measurement, 
and  another  leg  with  a  centring 
disc  for  scribing  circles  round 
holes.  Some  of  the  Starrett  fittings 
include  ball  points  for  striking 
circles  round  holes,  to  save  the 
trouble  of  bridging  across  them  and  marking  a  centre.  Thus  a 
single  leg  or  holder  carries  four  interchangeable  balls  of  iy\,  i,  f, 
and  I  in.  diameter. 

A  combination  tool  is  shown  in  Fig.  357,  in  which  compass 
and  caliper  legs  are  combined  in  one,  to  be  turned  about  on  their 
joints.  The  calipers  are  suitable  for  internal  and  external  work, 
and  the  compass  points  are  perpendicular. 


COMPASSES  AND  DIVIDERS.  267 


A  unique  attachment  to  a  tool  consists  simply  of  a  sliding 
grip,  two  of  which  can  be  bolted  to  caliper  legs.  Each  carries 
a  scribing  point,  to  be  used  as  a  compass  or  as  hermaphrodite 
calipers,  or,  as  they  are  more  generally  termed  here,  compass 
calipers ;  or  the  points  can  be  used  for 
measuring  the  bottoms  of  screw  threads,  or 
when  the  caliper  legs  are  extended  they  can 
be  used  as  trammel  points. 

The  tools  of  the  compass,  and  scriber 
type  all  owe  their  precision  value  to  their 
points,  to  the  fineness  of  which  is  due  the 
dimension  termed  the  “  thickness  of  a  line,” 
considered  a  fine  degree  of  accuracy  in 
handicraft,  and  is  of  course  the  finest 
measurement  available  in  the  system  of 
working  by  marking  out. 

The  limit  to  the  use  of  the  compass 
comes  in  when  the  legs  are  spread  very 
much.  They  should  not  be  used  to  their 
maximum  capacity,  because  the  angle  of  the 
legs  is  then  so  great  that  the  points  stand  further  from  perpendicu¬ 
lar  than  is  consistent  with  accurate  lining-out.  A  larger  pair  should 
then  be  substituted,  or  the  trammels  used.  It  is  well  to  curve  com¬ 
pass  points  inwards  to  correct  the  effect  of  setting  them  at  an  angle. 


0 


Fig.  358. 


Trammels  are  varied  in  regard  to  their  capacity  for  minute 
adjustments,  and  as  combination  tools.  The  common  form  com¬ 
prises  two  heads  with  fixed  points.  They  are  slid  along  the  beam 
(Fig.  358),  which  is  of  rectangular  section,  their  points  being  set 


268 


TOOLS. 


upon  the  rule,  and  pinched  by  thumb  screws  above,  which  press, 
not  directly  on  the  beam,  but  on  washers.  In  this  general  design 
of  common  trammels  the  heads  are  cast  in  brass.  These  are  suit¬ 
able  enough  for  nine-tenths  of  the  ordinary  work  done,  but  they 
lack  the  fine  adjustment  necessary  to  ensure  high-class  work. 
Every  one  who  uses  common  trammels  knows  how  difficult  it  is  to 
get  a  precise  result  without  a  good  many  pinchings  and  slackenings 
of  the  screw.  The  longer  the  bearing  which  the  heads  take  on 
the  beam  the  better,  in  reason.  The  pins  also  should  make  a 
perfectly  tight  fit  in  their  sockets,  either  by  a  driving  fit  or  by 
screwing.  In  the  best  instruments  one  of  the  heads  contains  pro¬ 
vision  for  fine  adjustment  by  means  of  a  screw,  variously  arranged, 
or  by  other  means. 

In  the  Starrett  trammels  fine  adjustments  are  effected  by  rotat¬ 
ing  the  points  in  their  sockets,  the  points  being  made  eccentric  rela¬ 
tively  to  the  shanks  for  the  purpose.  The  legs  pass  up  at  the  sides 
of  the  heads  instead  of  being  fitted  below  them,  and  the  upper 
projecting  portions  are  milled  for  the  fingers  to  rotate  them  by. 
These  are  also  combination  tools,  for  caliper  legs  fit  interchange¬ 
ably  with  the  points.  One  of  these  legs  is  jointed  at  the  com¬ 
mencement  of  the  curved  portion,  and  has  an  eccentric  thumb 
piece  for  effecting  fine  adjustments.  Two  special  forms  are  as 
follows : — 

One  is  a  light  extension  trammel,  the  beam  being  made  up  in 
three  sections,  each  of  14  in.  in  length,  either  of  which  can  be  united 
to  the  others  by  a  socket  coupling  and  grip  nut.  Both  points 
and  caliper  legs  are  fitted  into  the  heads.  The  latter  slide  on  a  bar 
of  circular  section,  flattened  on  one  side,  to  which  they  are  gripped 
with  a  knurled  nut  that  also  grips  the  slides  to  the  bar  and  the 
points  in  the  slides.  The  points  have  fine  adjustment  by  the 
eccentricity  imparted  to  them,  as  just  now  noted.  Friction  springs 
retain  them  in  place  when  the  knurled  nut  is  loosened. 

Another  trammel  has  the  heads  fitted  to  a  wooden  beam. 
As  in  the  first  example  named,  the  points  and  caliper  legs  pass 
up  at  the  sides  of  the  heads,  and  are  knurled  above.  Fine 
adjustments  of  the  points  and  caliper  legs  are  obtainable  by  the 
devices  previously  explained.  Two  pairs  of  points  are  fitted — the 
ordinary,  and  a  pair  of  extra  length  for  deep  work.  A  set  of  four 
ball  points,  with  a  holder  adapts  the  trammel  for  striking  circles 
round  holes  of  various  diameters.  In  another  type,  fine  adjust- 


COMPASSES  AND  DIVIDERS. 


269 


ment  of  one  leg  is  effected  by  hinging  it  to  a  lug  below  its  head, 
on  which  it  is  pivoted  by  a  knurled  nut  and  the  action  of  a  spring. 

In  one  form  of  beam  trammels,  and  also  in  parallel  dividers, 
the  long  milled  head  by  which  these  instruments  are  rotated  is 
used  for  clamping  the  heads,  which  has  some  advantages  over  the 


ordinary  thin  head  of  a  screw. 

In  one  type  of  precision  trammel  one  leg  is  fixed  near  one  end, 
being  pinched  with  a  screw,  and  the  other  is  adjusted  by  a  vernier 
along  a  beam,  graduated  in  millimetres. 

The  centring  balls  just  now  referred  to  are  useful  when  a  circle 
has  to  be  struck  round  a  small  hole.  When  holes  of  medium  and 
large  size  occur,  they  are  plugged,  or  else  bridged  with  a  strip  of 
wood  or  metal,  and  the  centre  located 
thereon.  But  in  the  case  of  small 
holes  this  can  be  avoided  by  using 
trammels  having  one  leg  formed  as  a 
solid  disc  of  parabolic  section  in  the 
vertical  direction. 

In  a  common  American  form  of 
trammel  the  beam  is  made  of  in. 
round  steel,  with  one  side  flattened. 

Circular  slides  are  pierced  to  carry  the 
points,  and  both  points  and  beam  are 
gripped  by  a  partial  turn  of  a  knurled 
nut.  In  those  trammels  in  which  fine 
adjustments  are  effected  by  having  the 
points  eccentric  to  the  axis  of  the  steel, 
friction  springs  retain  them  in  place 
while  the  nut  is  loosened. 

In  one  of  the  Starrett  trammels,  which  is  also  a  combination 


Fig-  359- 


tool,  the  heads  do  not  embrace  the  beam,  but  are  open-sided,  so 
that  a  beam  of  any  thickness  may  be  used,  and  of  any  depth  from 
f  to  if  in.,  that  being  the  range  of  adjustment  permitted  by  the 
clamping  screw,  The  points  pass  down  one  side  of  the  head,  and 
are  gripped  by  a  screw  at  one  side.  The  combination  comprises 
long  and  short  points,  two  pairs  of  caliper  legs  (inside  and  outside), 
and  a  set  of  four  ball  points,  which  cover  a  range  of  holes  up  to 
\\  in.  Fig.  359  shows  a  pair  of  light  trammel  heads,  which  are 
clamped  on  a  bar  at  any  desired  position.  They  are  suitable  for 
light  work,  and  will  do  delicate  marking. 


270 


TOOLS. 


A  connecting  link  between  the  dividers  and  trammels  is  the 
parallel  dividers  (Fig.  360).  In  these,  the  scribing  point  is  turned 
down  from  a  beam  which  slides  along  and  is  adjusted  in  a  perpen¬ 
dicular  stem.  The  advantage  of  this  design  is  that,  as  in  the 
trammels,  pressure  on  the  head  does  not  tend  to  spread  the  legs, 

*  but  comes  directly  over  the  centre  point. 

There  is  a  limit  to  the  length  of  trammel  beam  which  can 
be  used,  consistently  with  the  obtaining  of  precise  results.  The 

smaller  the  trammel  heads,  the  shorter  must 
the  beam  be.  Patternmakers  and  millwrights 
who  often  have  to  strike  large  radii  keep  a  set 
of  large  heads  for  the  purpose,  fitting  a  beam 
of,  say  1 1  by  if  in.,  or  2  by  ^  in.  cross  sec¬ 
tions.  Two  or  more  beams  of  different 
lengths  are  kept,  and  the  longest  is  stiffened 
by  cambering  it  on  the  top  edge,  starting  a 
foot  or  two  away  from  the  ends,  and  this  is 
sometimes  supplemented  by  screwing  cam¬ 
bered  strips  on  one  side  of  the  beam.  In 
this  way  rigid  but  light  rods  of  pine  from  12 
Fig.  360.  to  20  ft.  in  length  can  be  obtained,  beyond 

which  dimension,  radii  must  be  struck  by 
geometrical  methods  apart  from  the  aid  of  trammels. 

A  wooden  trammel  is  easier  to  make  than  one  of  metal,  and 
is  very  serviceable,  a  bit  of  boxwood  being  the  best  material.  The 
heads  will  be  turned,  rather  than  made  rectangular,  and  the  lower 
and  upper  portions  which  receive  the  leg,  and  the  screw,  bonded 
with  a  bit  of  ferrule.  A  nut  let  carefully  into  the  upper  portion  of 
the  head  flush  with  the  top  face  of  the  mortise  receives  the  thread 
of  the  set  screw. 


CHAPTER  XXIIL 

Calipers,  Vernier  Calipers,  and  Related  Forms. 

Essentials  in  Calipers— Proportions— Weight— Adjustability— External  and 
Internal  Types — Capacity  for  Adjustment,  how  met — Special  Forms — 
How  to  Use  Calipers — Examples — Compass  Caliper — Key  way  ditto — 
Vernier  Calipers— Principle  of  the  Vernier— Difference  between  Vernier 
and  Micrometer— Caliper  Rules— With  and  without  Verniers— Examples 
of  Vernier  Calipers — How  to  Read — Examples  of  Various  Forms. 

The  old-time  hands  never  had  so  rich  an  assortment  of 
calipers  as  that  which  is  offered  in  such  bewildering 
variety  to-day,  even  excluding  the  vernier,  and  micrometer 
calipers  which  form  separate  great  classes. 

It  is  the  custom  to  hold  calipers  in  less  esteem  than  formerly, 
due  to  the  fact  that  gauging  has  superseded  them  in  many  depart¬ 
ments  of  practice.  But  in  the  average  run  of  common  and  general 
work  they  must  always  retain  their  utility.  And  as  engineering 
practice  becomes  more  and  more  exacting,  increasing  care  is 
bestowed  on  the  design  and  construction  of  these  instruments, 
and  greater  care  and  refinement  in  handling  them  is  demanded. 

The  three  essentials  in  a  caliper  are  proper  proportions,  weight, 
and  adjustability.  In  the  ideal  forms,  both  of  outside  and  inside 
calipers,  proportion  and  weight  are  so  balanced  that  the  instru¬ 
ments  embody  the  minimum  of  elasticity  with  the  minimum  of 
weight.  Heavy  calipers  are  not  sensitive  enough  for  fine  measure¬ 
ments,  yet  stiffness  is  absolutely  necessary.  This  is  secured  by 
the  tapered  form  or  the  cantilever  style.  One  often  sees  home¬ 
made  articles  too  narrow  next  the  pivot,  and  too  broad  next  the 
points,  no  very  accurate  measurement  being  possible  with  these. 
Another  detail  is,  perfect  fitting  between  the  pin  and  its  hole,  and 
between  the  opposed  faces  around  the  pivot.  Another  is  fine 
points,  so  that  but  a  slight  surface  comes  in  contact  with  the  work, 
which  facilitates  reading  off  or  otherwise  testing  the  dimension 
taken. 


272 


TOOLS. 


'I'he  functions  of  the  external  and  internal  calipers  are  too 
obvious  to  call  for  remark  beyond  this — that  they  are  used  either 
to  measure  a  dimension,  and  test  it  on  a  rule,  or  against  another 
caliper,  as  inside  against  outside,  and  vice  versa.,  or  against  a  fixed 
gauge,  or  set  to  a  dimension  and  reducing  the  work  thereto. 
It  is  essential  that  the  frictional  hold  of  the  joint  shall  be  sufficient 
to  ensure  the  retention  of  the  legs  in  position  during  handling ; 
and  herein  lies  much  of  the  art  of  calipering — namely,  to  take 
dimensions  and  transfer  them,  or  check  them  without  alteration. 
In  large  heavy  calipers  a  mere  change  of  position  from  vertical  to 
horizontal  will  alter  the  measurement.  The  calipers  should  be 


Fig.  362. 


gripped  at  the  pivot,  not  by  the  legs,  when  in  use,  and  minute 
differences  in  size  are  produced  by  gentle  tapping  of  a  leg  on  the 
surface  of  any  object. 

This  brings  us  to  the  third  condition  named — that  of  capacity 
for  adjustment.  Numerous  devices  are  in  use  to  avoid  the 
method  of  adjustment  obtained  by  merely  tapping  the  legs,  though 
in  the  hands  of  a  careful  man  it  is  very  doubtful  if  any  device  is 
more  sensitive  than  that  of  the  sense  of  touch. 

An  old  method  is  one  borrowed  from  the  compasses — namely, 
a  slotted  quadrant  wing,  and  thumb  nut,  by  which  the  caliper  legs 
are  secured  in  any  position.  This  does  not  afford  any  exact 


CALIPERS. 


273 


means  of  adjustment,  but  only  security  of  fixing.  Such  calipers 
are  adjusted  with  light  taps,  with  the  wing  just  frictionally 
tightened. 

Minute  adjustment  is  provided  in  some  examples  by  a  compass 
device  also,  that  of  a  fine  adjustment  screw  at  the  termination  of 
the  quadrant  bar.  The  wing  nut  is  tightened  with  the  caliper 
legs  at  an  approximately  correct  position,  and  then  fine  adjust¬ 
ment  is  effected  by  the  screw. 

This  also  is  an  old  device ;  but  there  are  many  later  ones, 
some  of  which  are  preferable.  In  one  form  a  flat  washer  plate  is 
fitted  at  the  joint  of  the  legs,  and  is  extended  a  portion  of  the 
way  down  one  leg,  and  has  its  end  formed 
as  a  nut  in  which  an  adjusting  screw  mov¬ 
ing  parallel  with  the  face  of  the  leg  works 
(Fig.  361).  The  screw  is  carried  in  a  stud 
fastened  into  the  leg.  In  other  types  nuts 
are  used.  The  legs  are  connected  by  a  rod 
which  is  screwed  for  a  considerable  length 
like  the  screws  of  spring  dividers  (Fig.  362). 

But  instead  of  running  a  nut  back  over  the 
screw,  to  the  rapid  wear  of  the  latter,  and 
also  with  waste  of  time,  the  nut  is  both 
screwed,  and  plain  in  the  hole.  When  the 
legs  are  held  together,  releasing  their  end 
pressure  on  the  nut,  the  latter  can  be  slid 
along  by  the  smooth  portion  of  its  hole. 

When  the  pressure  due  to  the  spring  is 
allowed  to  come  on  the  nose  of  the  nut, 
the  threaded  portion  of  the  latter  engages 
with  the  screw,  and  fine  adjustments  can  be  effected  as  usual.  In 
another  form  of  caliper  a  lock  nut  is  used  to  retain  the  legs  in  the 
position  set.  Fig.  363  has  a  plain  solid  nut. 

There  are  many  instances  in  which  chambered  or  recessed 
portions  of  work  have  to  be  measured,  from  which  the  calipers 
cannot  be  withdrawn  without  shifting  their  legs.  A  device  to 
get  over  this  trouble  is  the  provision  of  an  auxiliary  wing,  which 
has  a  slot  into  which  a  stop  on  one  leg  is  pushed,  and  which 
ensures  the  same  setting  after  the  leg  has  been  loosened 
therefrom. 

Another  type  of  caliper  is  designed  for  reading  off  the  dimen- 


274 


TOOLS. 


sion  taken  by  the  legs,  on  a  quadrant  at  the  other  side  of  the 
pivot.  In  one  form  this  is  read  by  a  pointer  only,  but  in  others 
a  vernier  is  employed.  The  vernier  is  carried  in  an  extension  of 
one  of  the  caliper  legs,  and  moves  over  a  quadrant  carried  in  an 
extension  of  the  other  leg  (Fig.  364).  In  a  modification  of  the 
latter  a  locking  handle  is  fitted  to  the  pivot  (Fig.  365),  to  prevent 
risk  of  the  legs  being  shifted.  In  another  instrument  a  straight 
bar  takes  the  place  of  the  quadrant,  and  the  vernier  moves  over 
it,  the  bar  being  pivoted  at  one  end  (Fig.  366). 


To  use  calipers  properly  is  an  art  that  has  to  be  acquired,  and 
to  which  constant  practice  and  a  delicate  sense  of  touch  contri¬ 
bute.  Two  men  will  hardly  measure  the  same  piece  of  work 
exactly  alike,  as  so  much  depends  on  the  way  in  which  the 
calipers  are  handled. 

In  the  art  of  calipering,  a  good  man  will  be  safer  with  poor 
calipers  than  a  clumsy  one  with  the  best  instruments.  The  spring 
of  calipers  is  very  deceptive,  and  may  easily  lead  one  astray,  hence 
the  strength  of  the  case  for  fixed  gauges ;  yet  the  calipers  must 
ever  fill  a  place  of  their  own.  The  amount  of  spring  will  depend 


CALIPERS. 


275 


on  the  way  in  which  they  are  held — in  but  a  slight  and  almost 
imperceptible  degree  in  the  smallest,  but  very  perceptible  as  size 
and  weight  increase.  The  proper  way  to  hold  heavy  calipers  over 
work  is  perpendicularly  for  outside  work,  and  horizontal  for  inside, 
so  that  any  possible  drop  of  the  leg  due  to  weight  is  eliminated. 
Another  point  is,  that  in  whatever  position  a  pair  of  calipers  is 
held  (the  smallest  sizes  excepted)  to  take  a  dimension,  it  should 
be  held  similarly  when  checking  it  either  by  another  pair,  or  by  a 
rule.  It  is  more  necessary  to  observe  these  precautions  in  slender, 
springy,  badly-proportioned  tools 
than  in  those  with  good,  large,  well¬ 
fitting  joints  and  well-tapered  legs. 

It  is  easier  to  work  to  rule  di¬ 
mensions  by  the  aid  of  calipers  than 
to  produce  the  various  fits  required 
in  different  classes  of  work  by  them. 

Driving,  and  easy  fits  are  properly 
work  for  the  gauges,  because  the 
calipers  do  not  indicate  the  exact 
size  of  a  whole  circumference  as  do 
the  gauges.  When  these  fits  are 
tested  with  calipers,  the  internal  are 
tried  in  the  external,  and  the  degree 
of  tightness,  or  easiness  present  is 
the  means  by  which  the  workman 
estimates  the  measure  of  the  fit  for 
driving  hard,  as  in  press  fits  for 
exact  fitting,  or  for  free  fitting  as 
required  in  journal  bearings.  To 
measure  the  degree  of  contact  of  the 
fine  caliper  points  correctly,  no  coercion  or  pressure  must  be 
exercised  on  the  legs,  one  point  of  each  being  maintained  in  con¬ 
tact  by  leaning  them  against  the  forefinger  of  the  left  hand,  the 
other  points  being  moved  one  over  the  other. 

In  this  connection  the  double  calipers  may  be  mentioned — 
namely,  those  which  combine  external  and  internal  legs  respec¬ 
tively  on  opposite  sides  of  the  pivot.  The  design  gives  internal 
and  external  measurements  alike  at  the  opposite  ends.  But  they 
are  not  permanently  reliable  for  the  finest  work,  because  they 
wear  unequally.  For  common  use  they  fill  a  useful  place. 


276 


TOOLS. 


The  spring  of  calipers  is  utilised  by  the  workman,  turning 
what  is  an  evil  in  some  cases  into  a  blessing.  The  amount  of 
spring,  though  very  slight,  is  frequently  sufficient  to  enable  one  to 
judge  how  much  to  reduce  a  piece  of  work  as  it  nears  completion. 
Thus,  a  caliper  being  set  to  a  finished  diameter,  and  being  firmly 
jointed,  the  spring  due  to  forcing  it  over,  or  into  the  work  will 
indicate  a  full  dimension,  without  being  sufficient  to  shift  the 
setting  at  the  joint.  It  is,  in  effect,  the  same  as  the  difference 
between  the  “  go-on”  and  the  “  not-go-on  ”  of  the  fixed  gauges,  with 
the  difference,  that  in  the  hands  of  an  experienced  man  it  indicates 
by  just  how  much  the  work  must  be  reduced  to  bring  it  to  size. 
It  does  not  give  the  difference  in  hundredths  of  an  inch,  but  it  is 
none  the  less  efficient.  The  difference  between  a  tight  fit,  more 
or  less,  is  easily  recognised,  and  that  stage  at  which  the  calipers 
make  the  slightest  contact  without  the  exercise  of  force  and  with¬ 
out  slop  is  readily  detected. 

The  practice  of  trying  calipers  over  work  which  is  running  in 
the  lathe  is  one  that  is  often  adopted.  It  of  course  tends  to  wear 
the  caliper  points,  and  may,  when  roughing  down  is  being  done, 
shift  them  slightly.  But  when  testing  fine  finishing  dimensions, 
the  work  should  be  stopped  before  putting  on  the  calipers. 

Correct  measurement  can  only  be  ensured  when  calipers  are 
held  square  with  the  axis  of  the  work.  If  they  are  allowed  to  get 
across,  though  ever  so  slightly,  they  will  not  tell  the  true  diameter. 
To  detect  the  truth  of  the  right-angled  position  the  caliper  is 
steadied  on  one  point  and  moved,  or  the  attempt  is  made  to  move 
the  other  point  longitudinally,  to  see  whether  it  fits  easier  or 
tighter.  This  precaution  is  not  necessary  in  small  diameters,  but 
it  becomes  so  in  large  ones,  and  it  is  more  essential  is  checking 
internal  than  external  sizes.  An  illustration  of  a  similar  kind 
may  be  noted  in  the  rod  gauge  when  checking  the  bore  of  a  large 
cylinder. 

From  this  aspect  the  width  of  caliper  points  is  important. 
Some  workmen  like  wide  points,  because  they  tend  to  set  them¬ 
selves  square  across  the  piece  measured,  and  with  this  object  they 
are  often  spread  out.  These  are  all  right  for  average  work,  but 
not  for  the  finest.  They  are  useful  in  wood  turning  and  roughing 
down  metal,  but  not  for  much  besides.  If  wide  points  are  u.sed 
for  fine  precision  work,  the  unequal  wear  of  the  points  renders  it 
difficult  to  locate  a  dimension.  And  if  they  are  rounded  length- 


CALIPERS. 


277 


wise,  as  is  sometimes  done,  they  might  just  as  well  be  narrowed 
at  once. 

Another  way  in  which  calipers  are  used  is  to  employ  two  pairs, 
one  to  rough  down  by,  and  one  to  finish.  The  utility  of  this  plan 
comes  in  when  a  number  of  similar  pieces  have  to  be  turned  alike. 
In  such  a  case  the  locking  types  are  best,  because  they  are  not 
liable  to  accidental  alteration  in  size.  These 
are  then  employed  just  as  fixed  gauges. 

The  instrument  termed  a  compass  caliper, 
or  by  some,  hermaphrodite  caliper,  is  extremely 
useful.  It  is  a  scribing  tool,  the  caliper  leg 
controlling  the  movement  of  the  compass  leg. 

It  can  be  used  as  in  Fig.  367  or  Fig.  368.  In 
the  one  case — which  is  its  most  useful  applica¬ 
tion — its  caliper  point  is  brought  into  contact 
with  the  circumference  of  a  circle  at  various 
points,  and  its  compass  point  strikes  several 
short  lines,  the  intersection  of  which  indicates 
the  centre  of  the  circle.  In  the  other  applica-  Fig.  367. 
tion,  lines  can  be  drawn  parallel  with  any  sur¬ 
face,  external  or  internal,  curved  or  straight.  The  value  of  this 
tool  lies  in  the  greater  delicacy  of  contact  of  the  caliper  leg  over 
that  of  a  compass  point  if  used  for  the  same  purpose.  A  manu¬ 
facturer’s  form  of  this  instrument  is  shown  in  Fig.  369,  in  which 
the  caliper  end  is  double,  bent  to  right  and  left,  and  the  compass 

point  adjustable  for  length. 

Another  special  form  is  the 
keyway  caliper  (Fig.  370),  so  called 
because  it  is  used  for  checking 
the  distance  of  a  keyway  or  groove 
from  a  surface.  The  straight  leg 
is  inserted  and  lies  flat  against 
the  bottom  of  the  key  groove, 
while  the  caliper  point  checks 

At  this  stage  we  leave  the  calipers  of  the  types  hitherto  con¬ 
sidered,  for  these  alone  do  not  fulfil  the  requirements  of  present- 
day  manufacturing.  Extreme  accuracy  is  attained  with  these 
appliances,  but  not  extreme  precision  :  mutual  fitting,  but  not 
exact  absolute  dimensions.  For  these  we  must  go  to  the  vernier. 


its  depth  from  the  outside. 


278 


TOOLS. 


and  the  micrometer  calipers,  each  of  which  provides,  though  in  a 
different  fashion,  for  the  reading  off,  or  fixing  to  dimensions 
measured  in  hundredths,  and  thousandths  of  an  inch,  or  tenths,  or 
hundredths  of  a  millimetre.  These  tools  are  not  in  such  common 
and  general  use  as  the  calipers  already  noted,  though  they  are 
plentiful  in  shops  where  special  classes  of  manufacture  are  carried 
on,  and  in  tool-rooms.  They  are  too  fine  and  expensive  to  be 
knocking  about  on  every  ordinary  machine  and  bench,  for  which 
the  fixed  gauges,  to  be  considered  later,  are  more  suitable,  yet  in 
their  spheres  they  are  now  indispensable.  As  yet  they  are  chiefly 
manufactured  in  America,  Germany,  and  France. 


Fig.  369. 


The  methods  of  the  marker-out  form  a  very  important  section 
of  modern  as  of  the  older  practice,  since  in  many  classes  of  work 
they  cannot  be  dispensed  with.  A  man  with  a  scientific  turn  of 
mind  would  regard  them  all  as  coarse — akin  to  the  methods  of  the 
carpenter  and  joiner  and  mason,  as  in  some  degree  they  are.  But 
they  are  redeemed  from  the  imputation  of  coarseness  by  the 
methods  of  checking  which  follow.  It  is  substantially  correct  to 
say  that  no  decent  piece  of  work  is  ever  completed  by  reference 
to  the  lines  and  centre  pops  alone  which  are  laid  down  by  the 
marker-off  without  further  check.  In  fact,  we  must  regard  these 
in  the  highest  practice  as  simply  a  rough  approximation  to  the 
forms  and  dimensions  desired,  and  which  have  to  be  obtained  by 


CALIPERS. 


279 


devices  and  appliances  much  finer  than  those  employed  in  the 
mere  work  of  lining-out. 

In  considering  the  various  methods  of  checking  adopted  we 
must  remember  our  cardinal  subdivision  into  rule,  and  gauge 
measurement.  The  vernier  caliper,  or  caliper  rule,  and  the  micro¬ 
meter  caliper  each  combines  the  sense  of  touch  with  that  of 
vision— that  of  the  gauge  with  the  rule,— and  hence  these  two 
instruments  are  the  sheet-anchors  of  scientific  workshop  measure¬ 
ment,  having  many  applications,  not  only  to  the  actual  tools  used 
for  measurement,  but  also  being  embodied  in  precision  machines. 
An  explanation  of  these,  lying  as  they  do  at  the  basis  of  so  much  in 
modern  measurement,  should  preface  illustrations  of  the  instru¬ 
ments  in  which  they  are  embodied.  But  first  we  will  dispose  of 
the  caliper  rules. 

The  caliper  rules  of  plain  type  give  direct  readings  in  English, 
or  metric  measure.  In  the  plainest  forms  they  do  not  include  a 
vernier  reading,  but  a  slide  either  moves  along  a  graduated  edge, 
or  is  drawn  out,  and  is  itself  graduated,  in  addition  to  the  gradua¬ 
tions  on  the  edges  of  the  rule.  Such  rules  are  short— usually 
from  4  in.  to  8  in.  in  length,  and  rather  less  in  the  effective  caliper 
opening.  The  divisions  on  different  rules  are  made  in  a  wide 
range  to  suit  all  requirements,  English  and  metric.  They  are 
accurate  in  effecting  direct  readings  within  the  limits  of  the 
graduations,  to  fiqths  in.,  looths  in.,  or  half-millimetres,  but 
nothing  finer  is  practicable,  excepting  full  and  bare  dimen.sions. 
They  are  used  chiefly  for  ready  measurement  and  reference, 
sufficiently  accurate  in  general  work,  and  for  measuring  rods, 
tubes,  and  stock,  &c.  These  rules  without  a  vernier,  comprise  a 
large  number,  made  in  boxwood,  ivory,  brass  or  steel.  The  jaws 
are  more  liable  to  wear  than  the  high-class  articles  in  which  the 
jaws  are  of  steel  and  hardened. 

A  much  improved  form  of  sliding  caliper  is  illustrated  in 
Fig.  371.  The  beam  is  graduated  on  one  side  into  fiqths,  and  on 
the  other  to  looths,  of  an  inch.  The  section  of  the  beam,  seen 
in  end  view  to  the  left,  combines  strength  with  lightness.  There 
is  no  friction  or  wear  between  the  heads  and  the  scaled  faces. 
The  two  loose  heads  permit  of  fine  adjustments  by  the  locking  of 
the  right-hand  one  to  afford  resistance  to  the  slight  frictional 
movement  of  the  adjustable  jaw,  effected  by  the  milled  head. 

The  vernier  has  long  been  employed  in  astronomical  instru- 


280  ‘ 


TOOLS. 


merits,  having  been  invented  so  long  ago  as  1631  by  Pierre 
Vernier.  In  its  earlier  applications  it  was  made  with  one  gradua¬ 
tion  less  than  those  on  the  instrument  to  which  it  was  fitted — that 
is,  ten  of  its  subdivisions  were  equal  to  eleven  on  the  principal 
scale.  Later  it  was  made  with  one  graduation  more  than  the 
corresponding  portion  of  the  main  scale.  The  principle  is  the 


Fig-  371- 


same,  but  the  reading  is  rendered  easier.  The  vernier  in  the 
workshop  is  used  for  reading-off  dimensions  directly  to  a  thou¬ 
sandth  of  an  inch  by  the  inspection  of  the  unassisted  eye,  which 
could  not  of  course  be  done  by  simple  divisions  on  a  rule,  for 
which  one-hundredth  of  an  inch  is  extremely  fine. 

The  principle  of  a  vernier  is  illustrated  in  the  diagram  Fig. 

372.  A  represents  a  portion  of  a 
12  3  rule  having  its  inches  divided  into 

tenths;  b  the  vernier,  having  a 
length  of  nine  of  these  parts 
divided  equally  into  ten.  As  the 
sum  total  of  the  ten  divisions  on 
B  is  in.  short  of  i  in.,  it  follows 
that  each  division  on  b  must 
Fig.  372.  measure  10  x  10=  looth  of  an  inch 

less  than  the  divisions  on  a. 
Further,  if  the  line  i  on  b  is  in.  short  of  i  on  a,  then  line  2  on 
b  must  be  yfo  short  of  2  on  a,  and  line  3  on  b  in.  short  of 
line  3  on  A.  A  finer  degree  of  variation  can  be  obtained  by  either 
increasing  the  number  of  subdivisions  or  by  increasing  the  length 
of  the  vernier.  Thus  much  for  the  principle. 

The  micrometer  method  of  measurement  is  not  the  same  as 
the  vernier,  though  the  results  obtained  are  similar.  It  embodies 
the  minute  subdivision  of  the  pitch  of  an  accurately-cut  screw  of 


1  2  3 


CALIPERS. 


281 


fine  pitch  by  means  of  divisions  around  a  boss  that  encircles  the 
screw.  One  complete  rotation  of  the  boss  advances  the  screw 
through  a  length  equal  to  its  pitch,  and  of  course  a  portion  of  a 
revolution,  the  amount  of  which  is  regulated  and  read  off  on  the 
divisions  round  the  boss,  advances  it  by  a  fractional  portion  of  the 
pitch.  This  is  the  principle ;  the  differences  in  micrometer  cali¬ 
pers  are  those  only  in  detail,  such  as  to  ensure  perfection  of  the 
fitting  of  the  screw  in  its  nut,  and  to  compensate  for  wear,  and 
in  special  adaptations  of  the  micrometer  calipers  to  the  varied 
requirements  of  the  shops.  There  is  one  exception,  however,  to 
the  above — the  fitting  of  a  circular  vernier  to  calipers  for  extremely 
fine  measurements,  as  ten-thousandths  of  an  inch.  Details  of 
these  instruments  are  given  in  succeeding  pages. 

The  vernier  caliper  in  its  most  common  form  by  Brown  & 


Sharpe  is  shown  in  Fig.  373.  It  comprises  a  beam  or  bar,  two 
heads,  a  slide,  and  caliper  jaws,  both  internal  and  external.  The 
internal  jaws  are  recessed  to  clear  the  work,  leaving  a  compara¬ 
tively  short  length  only  for  the  working  faces,  which  are  hardened 
and  ground.  It  reads  to  loooths  of  an  inch,  or  64ths,  and  is  also 
made  to  read  to  5oths  of  a  millimetre. 

'Fhe  bar  a  is  divided  into  inches.  To  read  to  thousandths, 
each  inch  is  divided  into  ten  parts,  and  each  tenth  into  four,  so 
that  each  inch  is  subdivided  into  forty.  The  vernier  b  is  divided 
into  twenty-five  parts,  which  correspond  in  total  length  with 
twenty-four  parts,  or  twenty-four  fortieths  of  the  bar.  Each 
division  on  the  vernier  is  therefore  shorter  than  each  division  on 
the  bar  by  1 000th  of  an  inch.  The  same  relation  would  exist 
if  the  rule  were  divided  into  5oths  of  an  inch,  and  the  vernier 
have  20  lines  to  19  on  the  rule. 


282 


TOOLS. 


The  way  to  take  a  dimension  is  as  follows  : — In  the  type 
shown  in  Fig.  373  the^jaws  are  adjusted  by  hand  to  nearly  grip 
the  work.  The  thumbscrew  on  the  head  c  is  then  tightened,  grip¬ 
ping  the  head  on  the  bar.  That  on  the  head  d  is  tightened  only 
just  sufficiently  to  permit  fractional  movement  between  the  head 
and  the  bar.  The  screw  below  the  head  c  is  turned  by  its  milled 
head  to  move  the  sliding  jaw  d  along,  and  make  exact  contact 
between  the  jaws  and  the  work.  Then  the  screw  in  d  is  tightened 
further,  so  fixing  the  measurement. 

To  read  the  dimensions  so  obtained,  remember  that  if  the 
zero  point  on  the  vernier  corresponds  with  the  zero  point  on  the 
bar,  the  caliper  would  be  closed,  and  each  dimension  would  differ 
from  the  other  by  1 000th  of  an  inch  until  they  again  corresponded 
at  the  line  25  on  the  vernier.  When  the  caliper  is  set  open,  see 


how  far  the  zero  points  have  been  moved  from  one  another  in 
inches  and  parts.  Count  the  number  of  divisions  upon  the 
vernier  until  one  is  found  which  coincides  with  one  on  the  bar. 
Then  these  divisions  will  have  to  be  added  to  the  distance 
between  the  zero  points  read  off  directly  on  the  bar.  It  is  usual 
in  reading  to  call  the  tenths  ioo,oooths — 0.100,  and  the  40ths, 
or  fourths  of  tenths,  25,oooths — 0.025. 

To  set  the  calipers  to  a  dimension,  remember  that  when  the 
line  next  to  the  zero  line  on  the  vernier  b  corresponds  with  the 
line  next  the  inch  line  on  the  bar,  and  beyond  the  inch,  it  is  set 
to  loooth  of  an  inch.  If  set  to  the  line  within  the  inch  it  is 
1 000th  less  than  an  inch.  Hence  to  set  the  instrument  to  a 
definite  dimension,  count  the  number  of  divisions,  and  add  to  or 
subtract  these  from  the  nearest  whole  inches. 

Internal  dimensions  are  taken  by  the  jaws  a,  a,  which  are 


CALIPERS. 


283 


rounded  to  permit  them  to  enter  the  smallest  hole  which  they  , 
will  take.  Here  the  diameter  of  the  jaws  when  closed  must  be 
deducted  from  the  reading  taken  by  the  vernier.  This  diameter 
is  given  in  loooths  for  different  calipers. 

In  some  of  the  vernier  calipers  the  divisions  on  the  bar  are 
into  i6ths,  and  the  divisions 
on  the  vernier  are  eight  in 
in. ;  so  making  a  differ¬ 
ence  of  yys  one, 

in.  on  every  two,  and  so 
on.  Others  have  one  side 
graduated  thus,  and  the  side 
opposite  into  5oths,  with  the 
vernier  to  read  to  loooths. 

Fig-  374  is  a  German 
made  caliper  on  a  Brown  & 

Sharpe  model,  which  is 
divided  into  millimetres  on 

one  edge  and  into  inches  on  the  other.  It  embodies  inside  and 
outside  measurements.  The  screw  with  milled  head  on  the 
right  hand  head  affords  the  means  of  precise  adjustment  of  the 
right  hand  jaw. 

One  of  the  features  that  marks  some  German  vernier  calipers 


Fig.  376. 


is  the  substitution  of  a  spring  lever  for  locking  the  sliding  head, 
for  the  screw  pressing  on  a  spring  interposed  between  it  and  the 
beam.  One  of  these  is  seen  in  Fig.  375. 

In  a  French  vernier  caliper  (Fig.  376),  the  bar  is  trapezoidal 
in  section,  and  the  pressure  of  the  screw  is  taken  on  a  setting-up 
strip  a,  which  is  adjusted  with  two  set  screws.  The  horn  on  the 
bottom  of  the  movable  head  receives  the  pressure  of  the  thumb 


284 


TOOLS. 


in  making  adjustments.  In  a  lower  grade  of  vernier  caliper  of 
German  manufacture  (Fig.  377),  the  adjusting  head  is  omitted, 


Fig.  377- 


Fig.  379. 


and  the  head  and  vernier  are  moved  by  the  pressure  of  the  finger 
on  the  horn,  secured  by  a  screw  with  milled  head  beneath. 


CALIPERS. 


285 


A  special  form  of  vernier  caliper  is  illustrated  in  Fig.  378. 
A  pair  of  friction  rolls  is  a  substitute  for  a  micrometer  screw, 
in  making  adjustments  of  the  movable  blade.  These  rolls  bear 
by  their  edges  against  the  beam,  and  their  pressure  is  adjusted 
by  the  coiled  spring  and  two  milled  nuts.  The  sliding  head  is 
clamped  by  a  screw  above. 

A  good  many  vernier  calipers 
are  made  with  compass  points  (Fig. 

379),  prolonged  on  the  opposite 
side  to  the  jaws,  the  points  being 
screwed  in.  Compass  measurements 
may  thus  be  set,  or  read  off  with 
the  fine  precision  obtainable  by  the 
vernier.  In  some  instances,  as  in 
Fig.  380,  the  points  are  made  ad¬ 
justable  for  wear.  In  numerous  in¬ 
stances  the  bar  of  the  instrument  is 
utilised  as  a  depth  gauge,  a  set  of 
graduations  being  marked  from  the 
end  of  the  bar  farthest  from  the  head. 

In  some  vernier  calipers  the  cheeks  or  faces  against  which 
the  measurement  is  taken  are  made  separately  from  the  bodies. 
They  are  of  tee  section,  and  fastened  to  the  bodies  by  three 
screws  each.  The  advantage  is  that  these  alone  are  hardened. 


and  there  is  no  risk  of  the  jaws  becoming  fractured  by  being 
made  too  hard,  while  they  can  be  replaced  without  the  necessity 
for  making  new  jaws.  The  heads  are  prolonged  on  the  side 
opposite  to  the  jaws,  and  are  slotted  to  receive  steel  compass 
points.  The  beam  is  graduated  to  serve  as  a  depth  gauge. 
The  movable  jaw  has  an  eccentric  fitting,  by  which  it  is  clamped 


286 


TOOLS. 


to  the  beam,  locking  being  effected  by  depressing  a  lever.  The 
jaw  is  reversible,  so  that  it  can  be  used  as  a  marking  gauge  for 
parallel  lines.  A  small  circular  plate  is  provided  to  fit  on  the  end 
of  the  solid  head,  to  permit  of  the  instrument  being  stood  on  end 


and  used  as  a  scriber,  the  plate  sliding  on  a  surface,  and  the  point 
in  the  movable  slide  scribing  the  line. 

The  beam  calipers  are  also  made  in  inside  and  outside 
forms,  as  in  Figs.  381  and  382,  so  that  shafts  and  their  holes  can 
be  measured  while  the  caliper  indicates  the  size  of  both. 


CHAPTER  XXIV. 


Micrometer  Calipers. 

Principle  of  Design — Mechanism  of — Details  in  combination  with  Vernier — 
Taking  up  Wear — Various  Forms  Described — Horseshoe  Type — Beam 
Micrometer  Calipers — Screw  Thread  ditto — Gear  Teeth  ditto. 

The  principle  of  the  micrometer  caliper  is  simple,  but  the 
details  of  its  construction  call  for  a  high  degree  of 
mechanical  skill  and  care. 

The  Whitworth  measuring  machine  and  the  micrometer 
caliper  have  this  in  common,  that  fine  divisions  are  obtained  by 
subdividing  the  pitch  of  a  screw  by  means  of  a  micrometer  that 
contains  a  number  of  equal  divisions.  In  the  Whitworth  measur¬ 
ing  machine  the  screw  has  20  threads  to  the  inch.  It  is  turned  by 
a  worm  wheel  of  200  teeth,  actuated  by  a  single-threaded  worm, 
and  a  micrometer  wheel  on  the  axis  of  the  latter  has  250  divisions 
on  its  circumference,  so  that  a  movement  of  20x200x250  = 
1,000,000  in.  results  from  moving  the  micrometer  wheel  on  the 
screw  through  one  division.  In  this  machine  a  feeling  piece  with 
parallel  faces  is  introduced  between  the  end  of  the  work  to  be 
measured  and  the  sliding  piece.  The  difference  on  one  millionth 
of  an  inch  is  sufficient  to  cause  the  feeling  piece  to  be  suspended 
or  to  fall  of  its  own  gravity.  This  piece  in  later  measuring 
machines  by  the  Pratt  &  Whitney  Company  is  not  placed  in 
contact  with  the  work  to  be  measured,  but  caliper  jaws  are 
fitted  inside  one  of  the  headstocks  to  receive  it.  It  fulfils  this 
useful  function,  that  in  testing  standard  gauges  in  the  machine 
the  behaviour  of  this  piece  affords  an  indication  of  the  conditions 
of  pressure  between  different  gauges.  In  the  Pratt  (It  Whitney 
machines  a  variation  of  a  hundred-thousandth  of  an  inch  is  thus 
appreciable.  Machines  of  this  class,  which  cost  over  a  hundred 
pounds  each,  are  used  for  testing  only.  Pocket  micrometers  only 


288 


TOOLS. 


cost  from  a  pound  to  thirty  shillings,  reading  from  thousandths  to 
ten-thousandths. 

Fig.  383  illustrates  a  micrometer  caliper  to  read  to  thousandths 
of  an  inch.  It  embodies  a  screw,  concealed,  in  one  piece  with  the 
spindle  a,  having  a  pitch  of  forty  to  the  inch.  The  barrel  b  is  also 
graduated  forty  to  the  inch  on  a  line  parallel  with  the  screw. 


383- 


Each  graduation  therefore  equals  the  pitch  of  the  screw,  and 
therefore  the  distance  traversed  by  the  screw  during  one  revolution 
=  Y^oth,  or  of  an  inch.  The  thimble  c,  which  fits  the 

barrel  closely,  has  its  edge  bevelled  to  facilitate  reading  the 
divisions  there,  which  number  twenty-five.  Each  division  indi¬ 
cates  that  the  screw  has  made  -j^th  of  a  revolution,  consequently 


that  the  opening  of  the  caliper  has  been  altered  by  ^Vth  of  -^^jjth 
of  an  inch  =  "I’o  read  a  dimension,  therefore,  the  number 

of  divisions  visible  on  the  barrel  a  is  multiplied  by  25,  and  the 
number  of  divisions  on  the  bevelled  hub  of  the  thimble  is 
reckoned  from  zero  to  the  line  which  happens  to  correspond  with 
the  line  of  divisions  on  the  hub.  The  figure  illustrates  one  of  the 
Starrett  instruments,  which  has  a  knurled  piece  on  the  right-hand 


MICROMETER  CALIPER^. 


289 

end  of  the  thimble  by  which  the  rotation  of  the  screw  is  speeded 
about  three  to  one  for  making  rapid  adjustments.  The  spindle  is 
also  locked  in  any  position  by  the  knurled  nut  next  the  U-shaped 
arm. 

1  he  mechanism  of  the  Brown  &  Sharpe  calipers  is  illustrated  in 
Figs.  384,  385,  and  386,  the  first  representing  the  earlier,  the  second 
the  later  design.  In  Fig.  384  the  barrel  a  is  in  one  piece  with  the 
U-shaped  arm,  affording  greater  rigidity  than  was  secured  in  some 
early  types  in  which  it  was  screwed  into  the  arm.  The  rear  part  of 


Fig-  385- 


the  barrel  is  screwed  internally  to  form  a  long  nut  n,  through  which 
the  micrometer  screw  B  passes.  The  nut  is  split  longitudinally, 
and  encircled  by  a  tapered  clamping  ring  or  thimble  b  to  maintain 
a  close  fit  as  the  parts  become  worn.  A  wrench  c  is  used  for 
turning  the  ring,  to  get  at  which  the  thimble  a  is  run  off  sufficiently 
to  expose  the  ring.  The  spindle  portion  beyond  the  screw  b  is 
made  cylindrical  to  pass  through  the  boss  in  the  U-shaped  head, 
where  it  makes  a  close  fit,  and  this  and  the  enclosure  of  the  screw 
at  the  rear  end  protects  it  from  dust  and  injury.  The  anvil  c 

T 


2go 


TOOLS. 


makes  a  close  fit  in  its  l^oss,  in  which  it  can  be  turned  from  time 
to  time  to  compensate  for  the  wear  of  the  faces  against  which 
measurement  is  taken. 

In  the  improved  form,  Figs.  385  and  386,  more  detail  is  intro¬ 
duced,  but  the  screw  is  supported  better  along  its  length,  wear  is 
more  readily  taken  up,  and  a  clamping  device  fitted.  The  barrel 
A,  in  one  with  the  U-shaped  arm,  has  sundry  shouldered  recesses 
to  receive  various  sleeves  which  are  seen  in  place,  and  separately, 
similarly  lettered  in  Fig.  386.  Into  that  portion  of  the  barrel  farthest 
from  the  U  part,  at  the  enlarged  portion  a,  a  screwed  sleeve  b  fits, 
threaded  to  take  the  micrometer  screw.  Another  screwed  sleeve  c 
behind  this  assists  in  supporting  the  micrometer  screw  which  runs 
through  it,  and  in  taking  up  wear.  It  is  threaded  externally  to 
engage  with  an  internal  screw  cut  in  the  barrel,  and  with  one  in 
the  ring  d  which  abuts  against  the  end  of  the  barrel  and  forms  a 
lock  nut.  The  upper  end  of  c  has  an  angular  flange,  the  diameter 
of  which  is  the  same  as  that  of  the  barrel,  and  is  threaded  internally 
to  fit  the  micrometer  screw.  The  screw  threads  in  c  and  d  are 
finer  than  those  of  the  micrometer  screw,  as  being  more  suitable 
for  purposes  of  fine  adjustment.  The  plain  end  of  the  micrometer 
screw  is  encircled  by  a  ring  having  a  split  tapered  boss  threaded 
externally  on  the  taper  to  receive  a  sleeve  g,  threaded  to  fit  the 
taper,  and  having  a  knurled  head  coming  outside.  The  rotation 
of  the  milled  head  clamps  the  split  boss  around  the  screw  spindle, 
locking  it  in  position. 

Ordinary  micrometer  calipers  do  not  go  beyond  the  thousandth 
graduations.  But  lesser  readings  can  be  taken  by  subdividing  the 
twenty-five  divisions  around  the  thimble  and  judging  by  the  eye, 
so  that  half,  or  quarter  of  a  thousandth  can  be  estimated  pretty 
closely,  corresponding  with  the  “  full  ”  and  “  bare  ”  dimensions  so 
commonly  made.  But  a  thousandth  is  a  coarse  dimension.  This 
difference  in  external  and  internal  gauges  would  make  quite  a  slop 
fit.  If  fine  measurements  are  wanted,  a  circular  vernier  is  embodied 
in  the  caliper.  Ten-thousandths  of  an  inch  can  be  read  in  this 
way  by  the  eye  without  any  guessing  at  subdivisions.  These 
calipers  should  only  be  kept  for  the  finer  dimensions,  in  order  to 
avoid  excessive  wear,  which  would  soon  impair  their  accuracy  if 
used  indiscriminately  for  the  coarser  measurements. 

The  vernier  is  seen  in  Fig.  387  at  a  and  B.  There  are  ten 
divisions,  which  occupy  the  same  space  as  nine  divisions  on  the 


MICROMETER  CALIPERS. 


291 


6ARf?£L 

OI2rt>S9^8«0 

Uii 


TUff^BLE 

e/t  ff/?eL 
0«?C>S9Z860 

I  I  III 


thimble  (see  upper  Fig.  a).  When  a  line  on  the  thimble  at  a 
coincides  with  the  first  line  of  the  vernier,  the  next  two  lines  to  the 
right  differ  from  each  other  by  one-tenth  of 
the  length  of  a  division  on  the  thimble,  the 
next  two  by  two-tenths,  and  so  on.  When 
the  caliper  is  opened,  the  thimble  being 
turned  to  the  left,  the  passing  of  one  division 
by  a  fixed  point  on  the  barrel  indicates  that 
the  caliper  has  been  opened  a  thousandth  of 
an  inch.  Thus  when  the  thimble  is  turned  so  ^1 1  M  N  N^l  I  I  B 
that  a  line  on  it  coincides  with  the  second  1  i 

line  of  the  vernier,  the  thimble  has  moved  TM/^ece 
one-tenth  of  the  length  of  one  of  its  subdivi-  Fig.  387. 

sions — that  is,  one-tenth  of  one-thousandth, 
or  one  ten-thousandth  of  an  inch,  and  so  on.  To  read  the  caliper, 
therefore,  the  main  divisions,  or  thousandths,  are  read  off  as  usual ; 
then  the  number  of  divisions  on  the  vernier,  commencing  at  o, 
until  a  line  is  reached  which  is  coincident  with  one  on  the  thimble. 
One  ten-thousandth  is  added  for  each  division. 

The  difficulty  with  all  calipers  and  gauges  is  the  wear  of  the 
faces,  which  is  the  reason  why  line  measurements  instead  of  end 
measurements  are  adopted  for  all  ultimate  standards  of  reference. 
But  end  measurement  is  indispensable  for  ordinary  work,  and  the 
only  practical  device  for  instruments  required  for  constant  and 
ready  service.  In  the  micrometer  calipers  the  wear  causes  no 
inconvenience,  because  it  is  taken  up  at  the  anvil  end  by  readjust¬ 
ment  of  the  abutting  piece.  To  facilitate  this,  the  best  calipers 
have  a  standard  gauge  in  the  form  of  a  disc  i  in.  in  diameter,  for 
insertion  between  the  jaws  of  the  caliper. 

In  the  Bellows  micrometer  the  method  of  adjustment  is  that 
shown  in  Fig.  388.  Wear  on  the  screw  is  taken  up  by  a  nut 
encircling  the  screw,  and  tapered  on  the  outside  to  fit  a  taper  in 
the  barrel.  The  nut  is  split  down  one  side  and  partly  down  the 
side  opposite,  and  it  is  closed  by  turning  the  nut  a  behind  it,  forcing 
it  down  its  tapered  seating.  The  spindle  can  be  clamped  when 
set  by  a  split  bush  in  front,  closed  by  a  cam  pin  b.  The  anvil  is 
not  made  adjustable,  but  wear  on  its  face  and  on  the  spindle  end 
is  taken  up  by  adjusting  the  shell  or  thimble,  which,  when  done, 
is  secured  by  the  taper-headed  screw  c  expanding  the  end  of  the 
micrometer  screw  into  the  bushing. 


292 


TOOLS. 


In  the  Starrett  micrometer  and  some  others  there  is  no  adjust¬ 
ment  of  the  anvil,  but  the  shell  or  thimble  is  adjusted,  though  held 
in  a  different  manner  from  the  Bellows. 

The  Slocomb  micrometer  is  seen  in  Fig.  389.  In  this,  as  in 
some  others,  the  anvil  is  fixed,  and  adjustment  for  wear  is  made 


Fig.  388. 


c 


at  the  spindle  end.  The  screw  is  enclosed  at  the  front  end  by  a 
bush  A,  and  at  the  other  by  the  screwed  nut  b,  threaded  internally 
to  fit  the  micrometer  screw  of  40  P.,  and  externally  to  fit  the 
barrel  or  sleeve  with  another  pitch,  32  P.  The  reason  for  this  is 
to  permit  of  readjustment  for  wear,  since  by  turning  the  nut  b  the 


Fig.  389. 


spindle  will  be  advanced  by  the  difference  in  the  two  pitches.  As 
the  difference  in  an  entire  turn  is  six  quarter-thousandths,  the  adjust¬ 
ment  is  a  fine  one.  The  nut  b  is  solid,  which  is  claimed  as  an 
advantage  over  split  nuts,  as  there  is  no  possibility  of  dirt  getting 
through  to  the  screw,  which  may  happen  in  split  nuts. 

The  nut  c  is  used  for  adjustment,  which  it  effects  by  endlong 
movement  only,  so  bringing  opposite  sides  of  the  threads  in  each 


MICROMETER  CALIPERS. 


293 


nut  into  contact  with  the  micrometer  threads.  The  take-up  is  not 
effected  by  frictional  contact  alone,  but  by  fine  clutch  teeth  and  a 
coiled  spring.  There  are  fifty-six  V-shaped  teeth  milled  upon  the 
face  of  each  nut  b  and  c  to  engage  with  each  other.  To  take  up 


Fig.  390. 


slack,  the  micrometer  screw  is  turned  out  of  the  nut  b,  and  then  c 
is  turned  one  or  more  teeth  ahead.  An  even  tension  is  maintained 
between  the  two  by  a  very  fine  coiled  spring  occupying  a  recess 
between  the  two  nuts. 

Fig.  390  represents  a  German  micrometer  reading  to  hundredths 
of  a  millimetre.  The  objection  to  this  type 
is  that  the  screw  is  exposed  instead  of  being 
enclosed  and  protected  as  in  all  the  best 
articles. 

As  it  is  easy  to  vary  the  amount  of  pres¬ 
sure  exercised  on  so  delicate  an  instrument 
as  the  micrometer  caliper,  and  thus  obtain 
slightly  different  readings  in  taking  a  number 
of  measurements  of  similar  articles,  the 
ratchet  stop  by  the  Brown  &  Sharpe  Com¬ 
pany  is  devised.  Fig.  391.  It  comprises  a 
ratchet  and  spring  pawl  in  the  end  of  the 
stop,  which  forms  the  end  of  the  thimble. 

The  exercise  of  pressure  greater  than  that  at 
which  the  instrument  is  set  causes  the  ratchet  39 1- 

to  slip  past  the  pawl  and  stop  the  further 
turning  of  the  measuring  spindle.  In  opening  the  tool,  the  pawl 
catches  the  ratchet,  and  so  prevents  slip,  and  mnkes  the  ratchet 
stop  positive  in  its  return.  A  ratchet  stop  is  also  fitted  to  the 
Starrett  micrometers. 

It  is  usual  to  stamp  on  calipers  the  decimal  equivalents  of  one- 


294 


TOOLS. 


eighths,  one-sixteenths,  and  one-thirty-seconds  for  the  purpose  of 
ready  conversion.  Calipers  identical  in  all  respects  are  made  to 
metric  divisions,  reading  to  hundredths  of  a  millimetre. 

The  micrometer  calipers  are  made  in  many  styles  and  sizes. 
The  smallest  for  engineers’  use  measures  less  than  in.,  some  less 
than  ^  in.,  large  numbers  less  than  i  in.  Large  dimensions  are 

provided  for,  but  the 
standard  form  does  not 
go  beyond  2  in.  maxi- 


L..  J 


mum ;  and  then  the 


anvil,  instead  of  being 
a  short  piece,  generally 
^  equals  in  length  the  pro- 

Fig.  392.  jection  of  the  spindle, 

in  order  not  to  give  all 
the  overhang  to  the  latter.  A  clamp  screw  is  usually  fitted  to 
secure  the  anvil  firmly.  The  Starred  Company  make  an  attach¬ 
ment  (Fig.  392),  to  fit  over  the  anvil  end,  by  which  any  of  their 
2  in.  micrometers  can  be  converted  into  a  i  in.  micrometer.  It  is 
clamped  in  place  with  the  screw  seen  to  the  left. 

When  calipers  are  wanted  for  dimensions  above  2  in.,  or  at 
most  above  3  in.,  loose  measuring  points  are  fitted  to  lessen  the 


Fig.  393- 


overhang  of  the  spindle.  Only  a  limited  amount  of  movement  is 
given  to  the  screws  of  micrometer  calipers,  because  if  about  an 
inch  is  exceeded,  the  difficulties  of  preserving  their  alignment, 
&c.,  are  increased.  Yet  often  the  limits  of  such  a  caliper,  bar  its 
range  of  utility.  The  alternative  is  then  to  have  several  calipers, 
or  to  make  one  do  duty  for  several  by  the  insertion  of  loose 
measuring  points. 


MICROMETER  CALIPERS. 


295 


Calipers  are  made  specially  for  measuring  wire,  tubing,  sheet 
metal  and  paper,  and  other  fabrics.  In  most  instruments  the  ends 
of  the  anvil  and  the  spindle  are  bevelled  off;  in  a  few  they  are  not, 
but  the  ends  are  left  parallel  in  order  to  permit  of  measuring  up 
to  a  shoulder. 

A  convenience  in  handling  micrometers  is  a  ring  (Fig.  393), 


Fig.  394. 


provided  to  slip  the  second  finger  into,  while  the  thimble  is 
turned  between  the  forefinger  and  thumb.  In  the  micrometer 
by  the  Massachusetts  Tool  Company  the  i  and  2  in.  sizes  are 
combined  in  one  instrument,  but  without  removable  points  (Fig. 


394).  A  finger  ring  at  the  centre  makes  it  easy  to  handle.  In  this 
tool  the  spindles  do  not  rotate  as  is  usual  in  other  makes. 

A  useful  double  micrometer  is  made  (F'ig.  395),  on  the  same 
principle  as  the  go-on  and  not-go-on  gauges.  The  outer  micro¬ 
meter  measures  the  larger  size,  the  inner  the  smaller. 

There  is  another  type  of  micrometer  calipers  of  large  size,  of 
horse-shoe  shape,  going  up  to  about  1 2  in.  in  capacity.  Many 


296 


TOOLS. 


variations  occur  in  this  design.  In  the  Starrett  calipers  of  this 
type  the  micrometer  screw  has  i  in.  of  adjustment.  One  tail 
spindle  or  loose  measuring  point  does  duty  for  three  separate 
settings,  giving  a  range  with  the  micrometer  of  o  to  4  in.  in  one 
size,  of  4  to  8  in.  in  the  next,  and  of  8  to  12  in.  in  the  largest. 
The  spindle  is  set  by  means  of  fine  marks  ruled  i  in.  apart  on  it, 
and  by  which  it  is  clamped  in  the  arm  of  the  caliper. 

As  temperature  would  exercise  a  considerable  effect  in  large 
calipers,  the  steel  framing  is  covered  with  hard  fibre,  attached 
with  brass  screws,  which  acts  as  a  non-conductor  to  the  heat 
of  the  hands. 

In  the  Brown  &  Sharpe  instrument  of  this  type  three 
separate  measuring  points  are  fitted,  measuring  respectively  from 


3  to  4  in.,  from  4  to  5  in.,  and  from  5  to  6  in.  The  entire  range 
covered  is  from  3  to  6  in.  Each  point  when  inserted  is  secured 
with  a  knurled  nut,  and  lock  nuts  are  provided  to  compensate 
for  wear. 

Though  most  of  the  micrometer  calipers  are  designed  for 
measuring  short  lengths  only,  and  generally  under  2  in.,  outside 
of  these  there  is  another  type — the  beam  micrometers,  which  are 
used  on  a  similar  class  of  work  to  the  beam  vernier  calipers.  In 
these,  one  end  is  fast  at  one  end,  the  other  movable  along  the 
beam,  and  the  latter  carries  the  micrometer.  To  facilitate  the 
setting  of  the  movable  head  to  each  exact  inch  or  half-inch,  within 
the  range  of  the  instrument,  various  devices  are  adopted. 

Fig.  396  illustrates  the  beam  micrometer  by  the  Brown  & 


MICROMETER  CALIPERS. 


297 


Sharpe  Manufacturing  Company.  The  method  of  fine  adjustment 
of  the  movable  head  resembles  that  of  the  firm’s  vernier  caliper, 
the  block  a  to  the  right  being  clamped  with  the  head  in  its 
approximate  position,  and  the  head  b  adjusted  by  the  screw  and 
milled  head  c.  The  sliding  head  is  set  to  inches  by  lines  on  the 
bar,  seen  to  the  right,  a  line  d  on  a  chamfered  edge  on  the  head 


being  brought  to  coincide  therewith.  There  can  be  no  wear  in 
such  a  method  as  there  might  be  with  pins. 

In  the  Starrett  beam  micrometer  (Fig.  397),  the  movable  head 
is  set  at  each  inch,  from  i  to  6  in.,  by  inserting  a  plug  through 
the  head  and  beam.  The  special  feature  in  this  is  that  instead  of 
using  one  hole  only,  there  is  a  separate  independent  hole  for  each 
inch,  both  in  head  and  beam,  so  that  the  wear  is  divided  between 
all,  and  wear  in  one  hole 
would  not  affect  the  truth  of 
any  of  the  rest.  If  one  hole 
only  were  used  in  the  head, 
then  any  want  of  truth  in 
that  hole  would  impair  the 
accuracy  of  all  the  settings. 

It  is,  moreover,  easier  to  construct  the  caliper,  as  each  hole  is 
lapped  out  to  suit  its  own  setting,  and  no  regard  need  be  paid  to 
anything  else.  All  the  holes  are  bushed  with  steel,  hardened,  and 
lapped  to  fit  the  plug. 

In  the  Bellows  micrometer  steel  pins  are  inserted  at  in¬ 
tervals  of  ^  in.  in  the  beam,  a  hardened  steel  stop  in  the 
head  is  brought  against  either  of  these  stops,  and  when  set  is  held 


« 


298 


TOOLS. 


in  position  by  a  locking  screw  and  nut.  Afterwards  the  micro¬ 
meter  dimensions  are  taken. 

A  special  form  of  instrument  is  the  screw-thread  micrometer 
caliper,  by  the  use  of  which  the  diameters  of  threads  are  measured, 


Fig-  399- 


not  from  the  outside  diameter  directly,  but  from  the  sides  of  the 
threads.  The  top  of  a  thread  may  not  afford  a  sufficiently 
accurate  dimension,  but  the  sides'  should  do  so.  The  caliper 
therefore  fits  the  slope  of  the  threads,  and  so  measures  the  body; 


side,  and  as  the  pitch  diameter  c 
less  the  depth  of  one  thread,  the 


and  the  dimension  obtained  is 
not  the  normal  size  of  the 
thread,  but  the  pitch  taken  at 
half  the  depth,  'fhe  diagram 
Fig.  398  indicates  this.  The 
pitch  is  equal  to  the  full  size 
of  the  thread,  less  the  depth  of 
one  thread.  The  micrometer, 
Fig.  399,  is  so  graduated  that 
when  the  point  and  anvil  are 
in  contact,  as  in  Pdg.  398,  the 
caliper  is  set  at  o.  If,  there¬ 
fore,  the  caliper  were  opened 
\  in.,  the  points  «,  a  would  be 
just  I  in.  apart.  As  one  half 
the  depth  of  the  thread  is 
measured  from  the  top  on  each 
lals  the  full  size  of  the  thread, 
:pth  is  found  as  follows  : — 


Depth  of  V  thread.s  =  o.  866 -r  number  of  threads  to  i  in. 

Depth  of  U.S.  .standard  threads  =  0. 6495 number  of  threads  to  i  in. 
Depth  of  Whitworth  threads  =  0.64 -r  number  of  threads  to  I  in. 


MICROMETER  CALIPERS. 


299 


As  the  U.S.  standard  thread  is  flatted  ^  of  its  own  depth  on 
top,  it  follows  that  the  pitch  diameter  of  the  thread  is  increased  ^ 
on  each  side,  equalling  I  of  the  whole  depth  ;  and  instead  of  the 
constant  0.866,  the  Brown  &  Sharpe  Company  use  the  con¬ 
stant  0.6495,  which  is  I  of  0.866.  Tables  are  prepared  to  facilitate 
calculation. 

Another  special  caliper  is  that  for  measuring  gear  teeth,  their 
thicknesses,  and  the  depth  from  point  to  pitch  line  (Fig.  400). 
This  is  a  vernier  caliper,  having  a  vernier  to  both  thickness,  and 
de^th  slides.  It  reads  to  thousandths  of  an  inch. 


CHAPTER  XXV. 


Depth  Gauges  and  Rod  Gauges. 

Measuring  Depths,  and  Diameters — By  Rod  and  Rule — Applications  of  Micro¬ 
meter  and  Vernier  to — Forms  of  Depth  Gauges — Reading  Dimensions — 
Refinements  in  Design — Combination  Form — Rod  Gauges — Examples. 

The  measurement  of  depths  and  heights,  and  that  of  bores, 
is  generally  done  in  rather  a  crude  fashion,  although 
accurate  enough  for  the  work  of  an  average  shop. 

In  measuring  depths,  the  foot  rule  is  used  as  often  as  not,  the 
end  being  thrust  down  into  the  hole,  and  the  depth  read  off  on 
the  rule  on  its  edge,  or  by  passing  a  straight-edge  along  over  the 
face  of  the  work  across  the  nearest  divisions  of  the  rule.  Another 
way  is  to  pass  the  slide  of  the  slide  rule  down  into  the  hole,  letting 
the  end  of  the  rule  rest  on  the  face  of  the  work,  the  depth  to 
which  the  slide  projects  beyond  the  end  of  the  rule  being  read  off 
on  the  slide.  If  the  recess  is  open  on  one  or  more  sides,  or  if  its 
width  is  too  great  for  the  end  of  the  rule  to  bridge,  or  if  the  edges 
are  bevelled  or  shouldered  so  that  a  rule  cannot  be  brought  up 
close  to  them,  a  straight-edge  is  carried  across  the  top  face,  and  a 
pair  of  internal  calipers  tried  between  its  bottom  edge  and  the 
bottom  of  the  hole,  and  measurement  taken  from  the  calipers. 
Or  depths  may  be  taken  by  thickness  gauges,  if  such  are  available. 

To  take  internal  dimensions  such  as  diameters,  and  distances 
between  perpendicular  sides,  the  rod  gauge  is  the  common  device 
used  in  the  shops  The  rule  direct  is  used  very  often,  but  it  is 
not  possible  to  make  one  piece  fit  another  by  the  rule  alone — 
that  is,  one  could  not  measure  a  cylinder  bore,  and  turn  a  piston, 
ram,  or  plunger  to  fit  it,  by  reference  to  a  rule  measurement.  If 
a  dimension  is  started  from  the  end  of  a  rule,  that  end  soon 
becomes  worn  and  loses  its  truth.  If  a  dimension  is  taken  from 
the  first  inch,  there  is  sure  to  be  some  error  in  setting,  as  well  as 
in  reading  off  at  the  other  end.  For  these  reasons  a  rod  gauge 


GAUGES. 


301 


is  fitted  to  the  cylinder,  and  a  caliper  set  by  that  is  used  for 
turning  the  piston  or  plunger. 

The  rod  gauge  is  a  piece  of  round  steel,  from  ^  or  in. 
diameter  upwards,  according  to  the  length,  filed  at  the  ends  to  fit 
within  the  diameter,  and  tapered  towards  the  ends  to  reduce  the  area 
of  contact.  Measurement  is  then  taken  on  these  narrow  areas. 
The  rod  gauges  are  often  also  retained  as  permanent  records  of 
dimensions,  labels  being  tied  on  them,  giving  particulars  of  the 
wprk  to  which  they  belong.  In  taking  dimensions  with  these, 
they  are  moved  about  up  and  down,  and  tested  across  the  bore 
to  ensure  their  fitting  at  the  exact  diametral  position.  This  is  a 
very  necessary  precaution,  especially  on  large  bores,  where  a  false 
fit  may  easily  be  assumed  to  be  correct. 

These  methods,  in  the  light  of  modern  refinements,  may 
appear  open  to  the  objection  that  they  are  not  accurate  enough. 
Yet  they  are  quite  precise  enough  for  probably  nine-tenths  of  the 
volume  of  work  done  in  any  general  engineer’s  shop,  and  they 
are  not  in  any  degree  of  the  character  of  makeshifts.  In  fact, 
many  depth  gauges  that  are  manufactured  have  sliding  tongues 
like  those  of  slide  rules,  with  divisions  of  the  inch  on  them  ;  and 
many  internal  calipers  simply  have  plain  adjustments  of  the  rods, 
to  save  filing  solid  ends  to  length  for  every  separate  dimension. 

In  high-class  tools  of  these  kinds  the  micrometer  principle  and 
the  vernier  are  applied.  By  means  of  these,  dimensions  can  be 
read  in  thousandths  of  an  inch,  or  in  hundredths  of  a  millimetre, 
in  place  of  the  method  of  measuring  directly  with  a  rule,  or  with 
a  solid  rod.  In  these  instruments  the  design  is  that  of  the  calipers 
— namely,  a  barrel  graduated  lengthwise,  a  thimble  divided  around 
its  hub,  and  a  measuring  point  or  points.  Besides  this  we  have 
the  design  of  the  large  calipers  embodied — namely,  ready  settings 
to  large  dimensions,  apart  from  the  micrometric  ones,  as  half¬ 
inches,  to  increase  the  range  of  the  utility  of  the  tools. 

Depth  gauges  are  variously  made.  They  include  the  common 
kind  in  which  the  readings  are  direct,  as  in  the  rule ;  the  micro¬ 
meter  gauge,  and  the  vernier  gauge. 

The  common  gauge  (Fig.  401)  comprises  a  head  of  roughly 
triangular  outline,  the  base  of  which  rests  on  the  face  of  the 
work,  and  a  narrow  rule  which  is  slid  down  through  the  head,  in 
which  it  is  clamped  with  a  screw.  In  this  instrument,  which  is 
by  Brown  &  Sharpe,  the  face  of  the  head  is  bevelled  back  at  a 


302 


TOOLS. 


to  facilitate  the  reading  of  the  rule.  In  one  form  of  depth  gauge 
the  movable  stem  is  a'finely  threaded  pin  passing  through  a  half¬ 
nut  in  the  stock.  Coarse  adjustment  can  be  effected  by  turning 
a  milled  head,  which  releases  the  half-nut  and  permits  of  rapid 
sliding  of  the  pin  up  or  down.  On  throwing  in  the  half-nut,  the 
fine  thread  affords  the  means  of  adjustment.  In  these — of  which 
there  are  a  good  many  made — no  dimensions  are  marked.  The 
same  remark  applies  to  another  type  in  which  a  plain  round 
sliding  pin  is  used.  In  these  cases  the  depth  to  which  the  pin 
projects  has  to  be  measured  off.  These  are  useful  for  a  large 


range  of  work,  in  which  the 
rule,  or  slide  rule  would  be 
too  clumsy.  It  includes  a 
good  deal  of  that  done  by 
die  sinkers,  of  work  done  in 
lathe  and  drilling  machine, 
and  by  bench  fitters.  They 
are  very  cheap,  and  exceed¬ 
ingly  handy  instruments. 


A 


In  others  the  small 
round  sliding  gauge  rod  is 
retained,  but  provision  is 
made  for  reading  dimen¬ 
sions  on  the  tool.  In  the 
Sawyer  depth  gauge  the  rod 
is  of  circular  section,  fitting 
in  two  grooves  in  one  face 
of  the  stock — one  on  each 
side  of  the  clamping  screw. 


Fig.  401. 


P'ig.  402. 


The  two  grooves  have  each  i  in.  of  length  finely  graduated 
into  64ths  and  looths  respectively.  The  bar  is  divided  into  half¬ 
inches  only,  which  gives  full  readings,  while  the  fine  scales  give 
the  fractions  of  inches. 

The  Brown  &  Sharpe  micrometer  depth  gauge  (Fig.  402) 
measures  all  depths  and  heights  under  2|  in.  by  thousandths. 
The  screw  has  a  movement  of  in.  only,  and  all  equal  half¬ 
inches  are  therefore  adjusted  by  a  series  of  angular  grooves  in  the 
rod  A,  situated  at  distances  of  ^  in.  apart,  into  which  clamping 
fingers  at  the  end  of  the  thimble  are  sprung,  so  making  each  whole 
^  in.  adjustments  quickly.  The  same  design  is  made  to  measure 


GAUGES. 


303 


to  60  millimetres  in  length,  and  to  subdivide  to  hundredths  of  a 
millimetre. 

A  sectional  view  of  a  typical  depth  gauge,  with  micrometer 
adjustment,  is  shown  in  Fig.  403 — the  Slocomb.  It  is  a  com¬ 
bination  tool,  being  adaptable  for  use  as  a  rod  gauge.  The 
micrometer  section  is  at  a.  The  body  screws  on  the  foot  b  when 
used  as  a  depth  gauge.  For  use  as  a  rod  gauge,  the  foot  is 
unscrewed,  and  a  hardened  contact-piece  inserted  instead.  The 
rods  are  graduated  in  quarter  inches,  and  the  micrometer  reads 
to  thousandths. 

The  Brown  &  Sharpe  vernier  depth  gauge  (Fig.  404)  has  a 


Fig.  404. 


Fig.  403. 


head  of  tee  shape,  which  is  movable  on  the  rule  in  the  same  way 
as  the  vernier  caliper  made  by  the  firm.  The  fine  adjustment  of 
the  head  is  effected  by  the  second  head  above,  clamped  on  the 
rule  or  beam,  and  having  a  fine  milled-headed  screw  for  the  vernier 
movements.  It  reads  to  thousandths  of  an  inch  on  one  side,  and 
to  sixty-fourths  on  the  back,  and  takes  a  maximum  length  of  in. 

Fig.  405  is  a  German  vernier  depth  gauge,  without  the  pro¬ 
vision  for  fine  adjustment  of  the  last  example. 

The  vernier  is  applied  to  a  tool  that  fulfils  some  of  the  func¬ 
tions  of  a  scribing  block.  The  height  gauge  (Fig.  406),  as  it  is 
called  by  the  Brown  &  Sharpe  Company,  comprises  a  base  about 


304 


TOOLS. 


I  in.  wide,  to  afford  a  steady  support,  and  forms  a  fixed  end  or 
jaw.  The  movable  head  is  adjusted  finely  from  another  head 


Fig.  405. 


j'lB 

Fig.  407. 


clamped  to  the  bar,  just  as  in  the  vernier  calipers.  An  extension 
A  fits  to  the  movable  jaw  by  a  sliding  head  and  clamp  screw,  by 


GAUGES. 


305 


means  of  which  it  can  be  brought  out  to  varying  distances  from 
the  jaw.  Its  face  is  hardened,  and  the  outer  end  is  ground  to  a 
sharp  edge.  It  is  thus  used  for  locating  centres,  scribing  lines, 
or  checking  the  heights  of  faces  that  lie  beyond  the  end  of  the 
base.  The  instrument  admits  8  in.  in  height,  and  reads  to 
thousandths.  It  is  valuable  when  work  is  being  set  and  tooled 
on  machine  tables. 

Another  combination  tool,  shown  in  Fig.  407,  is  by  the  Massa¬ 
chusetts  Tool  Company,  in  which  a  depth  gauge  is  combined 
with  a  micrometer  caliper.  The  anvil  end  a  of  the  caliper  is  trued. 

*  The  steel  plug  b  is  inserted  through  the  anvil.  For  depth  reading, 
a  second  row  of  figures  is  stamped  on  the  divisions  on  the  barrel. 
The  divisions  on  the  thimble  serve  both  for  the  caliper  and  the 
depth  readings. 

A  form  of  micrometer  depth  gauge  is  shown  in  Fig.  408,  by 
which  the  height  of  a  surface  can  be  checked  from  a  plane  surface 
or  from  two  levels.  The  difference  is  given  in  hundredths  of  a 


Fig.  409. 


millimetre  between  two  levels.  To  take  up  wear,  the  tool  is 
placed  on  a  level  plane  and  the  barrel  adjusted  to  zero  when 
necessary. 

Inside  rod  gauges  are  of  two  kinds,  plain  adjustable,  and 
micrometric. 

The  Pratt  &  Whitney  Company  make  an  inside  gauge  of  the 
first  kind,  of  simple  construction  (Fig.  409).  A  tube  carries  a 
chuck  at  each  end,  and  these  are  tightened  round  the  split  ends 
of  the  tube  and  around  the  measuring  rods.  One  of  these  rods 
is  a  long  smooth  wire;  the  other  is  a  short  screwed  piece,  fitting 
into  a  tapped  hole  in  the  tube.  The  smooth  wire  affords  a  rough 
and  rapid  adjustment,  after  which  the  screwed  wire  permits  of  a 
fine  adjustment  being  made.  Range  in  diameters  from  small  to 
large  is  effected  by  changing  the  smooth  wires,  three  of  which  are 
furnished  with  each  gauge.  This  type  is  embodied  in  several 
other  gauges — that  is,  there  is  a  plain  rod  clamped  in  a  chuck  for 
coarse  setting,  and  a  screwed  end  or  anvil  for  fine  adjustments. 

u 


3o6 


TOOLS. 


Gauges  of  these  hinds  are  made  in  various  capacities,  usually 
with  three  rods  to  interchange  in  the  body,  giving  lengths  ranging 
from  3  in.  in  the  shortest  to  6|  in.  in  the  longest  in  one  size,  and 
from  6  in.  in  the  shortest  to  i6  in.  in  the  longest  in  another  size. 
These  gauges  being  adjustable  only,  and  not’ micrometric,  measure¬ 
ment  is  taken  by  reference  to  any  convenient  standard. 

I'he  bodies  are  knurled,  and  the  ends  of  the  rods,  or  rather 


Fig.  410. 


wires  are  hardened.  The  wires  measure  about  g-  in.  only  in 
diameter,  and  the  entire  weight  is  but  a  few  ounces. 

Ill  the  inside  micrometer  rod  gauge,  definite  dimensions  are 
read  off  to  thousandths  of  an  inch,  or  in  the  metric  gauge  to  one- 
hundredths  of  a  millimetre.  The  micrometer  screw  usually  has 
a  movement  of  |  in.,  and  extension  rods  supply  the  means  of 
increasing  the  dimensions  by  half  inches.  In  the  Brown  & 
Sharpe,  the  rods  themselves  vary  from  each  other  by  |  in.  In  the 


A 


Starrett,  lines  are  marked  upon  the  rods  at  distances  of  |  in. 
asunder.  To  maintain  these  lengths  intact,  each  rod  in  the  latter 
gauge  has  an  adjustable  hardened  steel  anvil  in  its  end.  In  the 
former,  adjustment  is  by  means  of  nuts — an  adjusting  nut  and 
a  check  nut.  The  Brown  &  Sharpe  inside  micrometric  gauge 
has  a  screw  with  a  movement  of  ^  in.,  and  the  extension  rods, 
varying  by  ^  in.,  enable  measurements  to  be  taken  from  3  to 
6  in. 

A  rod  gauge  by  Durand  &  Company  in  shown  in  Fig.  410.  . 
Fig.  41 1  is  a  special  form  by  the  Sawyer  Tool  Company.  It  has 


GAUGES. 


307 


a  large  graduated  head,  over  which  a  steel  arm  a  projects  to  form 
the  reading  point.  The  reading,  can  be  set  by  the  screw  b,  which 
locks  the  micrometer  screw  by  a  brass  pad.  A  taper  bolt  at  the 
other  end  locks  the  extension  rods,  which  are  of  in.  steel  rod, 
and  the  cap  shown  is  slipped  over  the  end  and  secured  with  the 
screw,  thus  forming  a  hardened  measuring  end. 

In  a  French  internal  gauge,  the  plain  movable  point  is  clamped 
with  a  milled-headed  screw  through  lugs  on  the  barrel,  which  is 
split  at  that  locality.  The  micrometer  ad¬ 
justment  is  at  the  other  end. 

Woodworkers’  gauges  can  be  ranked 
under  two  classes,  marking  and  cutting. 

The  first  mark  lines  by  which  to  plane 
or  chisel,  the  second  sever  very  thin  strips 
of  stuff  in  place  of  sawing.  Both  forms 
adjustable  on  the  sleeves,  and  fastened 
with  a  thumb  screw.  The  essential 


Fig.  412. 


have  their  heads 
with  a  wedge,  or 
difference  lies  in  the 
marker,  or  nicker,  or  cutter,  the  first  being  very  fine,  the 
second  broader  and  chisel-like  in  character.  The  mortise 
gauge  is  a  marking  gauge,  but  it  stands  as  a  class  by  itself.  Its 
peculiarity  lies  in  the  fact  that  it  has  two  markers,  one  fixed,  the 
other  movable,  with  a  screw,  so  that  it  can  be  set  to  any  width  of 


Fig.  413- 


m  m  m  m  nr 

I  *  *  *  s  >  *  _  H  I  Brn  *  * 


Fig.  414. 


mortise  required,  besides  which  the  head  is  adjustable.  The 
head  is  generally  faced  with  slips  of  brass  to  present  a  good 
wearing  surface. 

Fig.  4 1  2  shows  the  usual  type  of  woodworkers’  gauge,  either 
for  marking  or  cutting,  the  difference  between  the  two  consisting 
only  in  the  form  of  the  cutting  portion. 

Fig.  413  shows  a  shop-made  gauge,  termed  a  long-tooth  gauge. 
Both  the  stem  a,  and  the  marker  d,  are  capable  of  adjustment, 
and  setting  with  wedges,  to  render  the  gauge  adaptable  for 


3o8 


TOOLS. 


marking  on  surfaces  that  do  not  stand  at  right  angles  with  each 
other. 

Fig.  414  shows  a  specimen  punch,  which  we  class  with  gauges, 
because  it  marks  the  gauge  points  on  specimen  test  pieces,  so 
supplying  the  means  of  measuring  the  amounts  of  elongation  at 
different  portions  of  the  pieces. 


CHAPTER  XXVI. 


Snap,  Cylindrical,  and  Limit  Gauges. 

Horseshoe  Calipers — Difference  between  Standard  and  Limit  Gauges — The 
Newall  System  —  Provisions  against  Wear  —  Accuracy  of  Cylindrical 
Gauges— and  Horseshoe  ditto — Examples  of  Gauges — Plug  and  Ring — 
Snap  Gauges. 

WE  leave  now  the  various  calipers  and  gauges  with  mov¬ 
able  jaws,  to  consider  those  in  which  the  jaws  are 
rigidly  fixed.  These  instruments  were  used  when  the 
writer  was  an  apprentice,  but  they  were  mostly  shop-made  articles, 
and  at  that  time  the  very  high-class  fine  precision  tools,  and  the 
system  of  which  they  form  a  part,  were  practically  unknown  in 
English  shops.  The  horseshoe  calipers  were  the  forms  familiar 
at  that  time,  and  were  used  for  very  lar^e  as  well  as  for  medium 
dimensions.  They  were  made  of  a  piece  of  flat  bar  bent  round 
in  the  smithy,  and  filed  to  the  rule,  or  to  another  gauge.  Though 
a  rough  and  crude  form,  they  were  yet  in  advance  of  previous 
practice,  and  the  working  “  full  ”  and  “  bare  ”  to  these  might  be 
considered  as  the  antecedents  of  the  present-day  limit  gauges. 
From  those  a  large  family  of  gauges  have  descended,  but  the 
principle  underlying  all  is  the  unalterable  dimensions  of  instru¬ 
ments  of  this  class. 

Tools  of  this  kind  embrace  not  only  the  fixed  calipers  (inside 
and  outside),  now  termed  the  “snap  gauges,”  but  also,  cylindrical 
gauges  (internal  and  external),  screw  thread  gauges  (internal  and 
external),  and  also  the  limit  gauges,  and  the  standard  end  measure 
test  pieces  and  rods,  as  well  as  the  reference  discs,  which  are 
not  for  workshop  use,  but  for  checking  the  fixed  gauges  by.  And 
the  price  of  these  articles  is  regulated  by  the  degree  of  approach 
to  absolute  accuracy  which  they  make. 

The  difference  between  a  standard  gauge,  and  a  limit  gauge 
is  a  very  important  one  in  modern  workshop  economies.  A 


310 


TOOLS. 


standard  is  one  that  is  practically  exact  to  size,  neither  being  more 
nor  less  than  the  specified  size ;  a  limit  is  one  that  is  both  larger, 
and  smaller  than  the  standard  by  a  predetermined  amount.  In 
working  with  a  standard,  tight  fits,  and  easy  fits  are  made  by  the 
discretion  of  the  workman,  working  full,  and  bare.  In  working 
with  limits,  the  gauge  fixes  the  degree  of  tight,  or  easy  fits,  by  the 
amount  of  difference  between  the  size  of  its  two  ends,  predeter¬ 
mined  in  the  manufacture  of  the  gauge.  The  workman  would 
experience  infinite  trouble  in  producing  interchangeable  work  by 
the  first  named;  the  second  renders  such  a  task  comparatively 
easy.  And  not  only  in  fine  finishing,  but  in  roughing  down  work, 
to  be  finished  by  grinding,  the  latter  are  invaluable  aids. 

The  modern  system  has  gone  far  beyond  the  original  one. 
The  plug  and  ring  gauges  were,  and  are,  made  in  two  sets,  for 
tight,  and  easy  fits  respectively.  As  a  rule,  however,  in  the  older 
practice,  the  plug  was  just  made  to  fit  the  ring,  if  a  film  of  oil 
was  applied,  and  the  only  limits  were  those  which  were  due  to 
the  workman’s  sense  of  touch.  But  practically  the  departures 
from  exact  fits  which  are  required  in  shops  are  infinite.  A  tight 
fit  may  be  very  tight  indeed — so  tight  that  it  takes  the  place  of 
keying,  or  it  may  be  supplemented  by  keying ;  a  running  fit  will 
vary  with  classes  of  machines,  ranging  from  the  roughest,  to  the 
finest  instruments  of  precision.  There  is,  for  instance,  a  wide 
difference  between  the  fitting  of  the  shafts  and  bearings  of  a 
common  winch  or  crane,  or  of  a  mortar  mill,  or  of  horse  gear, 
and  that  of  a  high-class  machine  tool  of  any  kind.  The  value  of 
the  modern  system  of  gauging  is  immensely  enhanced  by  the  fact 
that  the  exact  limits  of  “tolerance”  which  are  desirable  in 
different  classes  of  work  are  embodied  in  the  gauges  which  are 
designed  specially  for  each  class.  As  such  an  arrangement  would, 
if  carried  out  to  its  fullest  utilities,  demand  a  large  number  of 
gauges,  the  Newall  system  has  been  devised,  by  which  a  large 
number  of  gradations  can  be  obtained  by  the  adjustments  of  the 
gauges,  and  so  the  number  of  instruments  is  brought  within 
reasonable  limits.  Standard  plugs  are  employed  to  set  them  by, 
in  combination  with  a  graduated  dial,  and  index  plate,  by  which 
the  exact  limits  required  for  each  class  of  work  are  fixed.  In 
these' gauges  (Fig.  428,  p.  315),  four  classes  of  fits  are  taken — ■ 
force  fits,  driving  fits,  push  fits,  and  running  fits ;  and  the  latter 
are  divided  into  three  groups,  so  that  there  are  six  groups  or 


GAUGES. 


3” 


classes,  besides  standard  holes,  tabulated.  In  each  of  these, 
again,  the  limits  of  tolerance  vary  with  the  size  of  holes,  being 
wider  as  the  sizes  of  holes  increase. 

The  wear  of  gauges  has  to  be  guarded  against.  In  the  older 
shop  system  ring  gauges  were  readjusted  in  a  rather  crude  fashion 
by  heating  and  quenching  them,  repeating  the  operation  two  or 
three  times  if  necessary.  This  had  the  effect  of  reducing  the  size 
of  the  hole.  Horseshoe  gauges  were  set  inwards  by  the  hammer. 
In  the  case  of  high-class  instruments  for  fine  precision  work,  it  is 
preferable  to  make  new  gauges,  the  old  ones  being  reground  to 
the  next  size.  The  Newall  system  provides  against  this  by 
providing  what  is  practically  a  new  gauge  for  each  job. 

Cylindrical  gauges  are  made  accurately  within  dimensions 
ranging  from  to  yowir  inch,  with  considerable 

differences  in  price.  The  yovocr  sufficiently  fine  for  all 
ordinary  work,  the  yy^xj-o  being  used  for  high  classes  of  work. 
An  illustration  of  the  manner  in  which  gauge  making  is  done  is 
afforded  by  the  statement  that  a  number  of  lots  of  cylindrical 
gauges  were  “roughed  out”  to  within  about  of  an  inch; 

eighteen  months  afterwards  a  similar  lot  were  roughed  out,  and 
the  plugs  and  rings  in  both  sets  were  found  to  interchange  with 
each  other. 

The  ring  gauges  do  not  give  quite  the  accurate  results  which 
may  be  obtained  by  fixed  calipers  of  the  horseshoe  or  similar 
types.  The  reason  probably  is  that  the  surfaces  in  contact  are 
larger  in  the  first  case  than  in  the  second.  This  perhaps  should 
make  no  difference,  provided  the  extent  of  the  contact  and  the 
degree  of  friction  were  exactly  alike  in  all  portions  of  the  circum¬ 
ference  and  length  of  the  ring  gauges.  This  seems  to  be 
paralleled  by  the  difference  between  wide  and  narrow  pointed 
calipers,  and  that  between  rod  gauges  with  wide  and  narrow 
points.  Always  the  finest  results  are  obtained  by  narrow  pointed 
instruments.  And  the  fact  is  undoubted  that  the  horseshoe 
gauges  are  capable  of  detecting  variations  which  the  ring  gauges 
cannot  do.  With  a  2  in.  ring  gauge,  a  variation  of  xofott 
inch  cannot  be  detected,  while  a  caliper  gauge  adjusted  to  a  2  in. 
standard  cylindrical  gauge  will  show  it. 

We  are  dealing,  of  course,  with  extremely  fine  measurements 
— so  fine  that  they  have  but  a  distant  relation  to  the  everyday 
work  of  the  ordinary  shop.  Yet  there  are  departments  of 


312 


TOOLS. 


engineering,  and  instrument,  and  watch  making  in  which  they  find 
their  place.  And  behind  it  there  is  the  subject  which  deals  with 

the  methods  by  which  such  fine  dimen¬ 
sions  are  obtained.  In  the  work  of 
gauge  making  a  thousandth  is  too 
coarse  to  be  dealt  with.  If  a  plug 
gauge  one-thousandth  of  an  inch 
smaller  than  the  ring  is  inserted,  it  is 
a  slop  fit.  In  close  gauged  fits  the 
plug  cannot  be  inserted  in  the  ring 
without  an  application  of  good  oil,  and 
if  it  is  allowed  to  remain  stationary  for 
even  a  few  seconds  the  two  will  seize 
and  become  a  driving  fit.  A  man  who 
is  accustomed  to  handling  such  fine 
gauges  will  treat  them  rather  freely 
without  seizing  occurring,  while  one 
not  used  to  the  work  will  get  them 
seized  almost  immediately.  There  is  a 
knack  in  using  them,  and  a  delicate 
sense  of  touch,  and  movement  of 
the  wrist  which  can  only  be  ac¬ 
quired  by  practice.  In  standard 
gauges  a  margin  of  but  a  few  ten- 
thousandths  is  permissible. 

A  few  examples  of  the  principal 
designs  in  which  these  are  manufactured  are  given  in  subsequent 
illustrations. 


Fig-  415- 


Fig.  415  is  the  plug  and  ring  gauge,  differences  being  made  in 
the  form  of  the  handle  by  different  firms.  Fig.  416  is  the  limit 
plug  gauge,  with  its  minus  and  plus  marks,  corresponding  respec¬ 
tively  with  the  “  go  in  ”  and  “  not  go  in  ”  fits.  Generally  now  the 


GAUGES. 


313 


latter  end  is  made  rather  shorter  than  the  former,  so  that  the 
workman  can  tell  at  a  glance  which  end  he  is  using. 

Fig.  417  represents  the  Rogers  gauges,  with  handles.  These 
are  exact  fits — that  is,  with  no  limits.  The  dimensions  in  which 
they  are  made  range  from  ^  in.  to  6  in.  They  are  made  in  two 


classes,  one  with  a  limit  of  error  of  l^e  other  within 

another  type,  the  internal  and  external  gauges  are 
combined  in  one  bar  (Fig.  418),  and  made  either  exact  or  to 
limits.  Figs.  419  and  420  show  some  German  gauges,  made  of 
hardened  cast  steel,  and  guaranteed  within  limits  of  plus  and 
minus  0.005  gauges  are  illustrated  in 

Fig.  421.  The  Billings  &  Spencer  drop  forged  gauge  is  seen  in 


TOOLS. 


3M 

Fig.  422.  They  range  from  ^  to  2^  in.  Two  forms  of  limit 
gauges  by  the  Rogers  Company  are  shown  in  Figs.  423  and  424, 


Fig.  422. 

the  first  being  the  common  type,  the  second  containing  two  sets  of 

dimensions  in  one  gauge, 
both  plus  and  minus. 
Fig.  425  is  a  Brown 
&  Sharpe  limit  gauge 
made  of  plain  flat  bar. 

Fig,  426  is  one  of 
the  Loewe  snap  gauges 
made  from  forgings  up 
to  4  in.,  and  above  that 
size  in  cast  iron.  The  illustration  shows  how  the  working  faces  are 
formed,  being  of  steel  in¬ 
serted,  and  pinned  in  place, 
hardened  and  ground,  and 
lapped  by  hand.  A  some¬ 
what  similar  device  is 
shown  in  Fig.  427,  which 
illustrates  the  fitting  of  a 
hardened  steel  anvil  in  a 
body  of  forged  steel.  This 
is  by  a  French  firm.  Fig. 

428  is  one  type  of  the 
Newall  gauge.  It  has  two 
pairs  of  measuring  points 
to  give  the  limits,  which  are 
adjusted  by  a  series  of  steel  standard  bars.  When  the  adjusting 
screws  are  set,  they  are  locked  by  the  tightening  screws. 


Fig.  423. 


GA  UGES. 


315 


Fig.  427. 


Fig.  428. 


The  fixed  gauges  themselves  have  to  be  checked  as  they  wear, 
and  so  finer  gauges  are  prepared  solely  to  check  the  working 
instruments.  There  are  end  measure  pieces,  discs,  and  stepped 


3i6 


TOOLS. 


gauges,  of  which  Fig.  429  shows  one  form.  These  are  generally 
brought  to  within  about  one  fifty-thousandth  part  of  an  inch  of 
absolute  accuracy.  Being  kept  as  checks  only,  wear  is  practically 
nil. 

Ring  gauges  may  be  tested  by  inserting  two  or  more  plug 
gauges  across  the  diameter,  when,  if  right,  they  will  hold  tightly 
together,  just  filling  up  the  hole.  This  is  a  similar  device  to  that 
which  was  adopted  by  the  Pratt  &  Whitney  Company  in  the 
manufacture  of  their  gauges.  A  number  of  end  measuring  pieces 


Fig.  429. 

were  prepared  from  accurate  subdivisions  of  the  yard,  and  rang¬ 
ing  by  sixteenths  from  j  to  4  in.  in  length.  These  were  taken  at 
random  in  numbers  sufficient  to  make  up  a  foot  in  length,  and  so 
made  to  test  each  other.  A  variation  of  only  a  thirty-thousandth 
of  an  inch  in  each  would  have  vitiated  the  results,  being  a  thick¬ 
ness  equal  to  that  of  the  finest  gold  leaf,  which  will  float  in  the 
air.  The  ends  of  the  standards  are  so  finely  polished  that  they 
will  support  each  other  by  their  ends,  similarly  to  the  best  made 
surface  plates. 


CHAPTER  XXVIL 


Screw  Thread,  Wire,  and  Reference  Gauges. 

C'lauges  for  Grinding  and  Setting  Screw  Thread  Tools — Thread  Gauges — 
Combination  Forms — Reference  Gauges — Pipe  Threads — Gauges  for 
Holes  for  Screwing,  and  for  Keyways — Wire  Gauges. 

There  are  a  large  number  of  fixed  gauges  besides  those 
already  illustrated,  for  special  purposes,  used  for  angles, 
screw  threads,  wire,  sheet  metals,  &c.  Those  used  for 
screw-cutting  form  a  large  class.  The  following  are  some  of  the 
most  common  : — 


The  gauge  for  grinding  and  setting  screw-thread  tools  (Fig. 
430),  is  made  with  angles  of  60°  for  United  States  standard  and 
metric  threads,  and  for  lathe  centres,  and 
to  angles  of  55°  for  Whitworth  standard. 

This  little  appliance  is  used  for  checking 
the  angle  to  which  a  tool  for  cutting 
screw  threads  should  be  ground,  and  for 
setting  the  tool  truly  both  for  external  and 
internal  threads,  and  also  for  testing  the 
truth  of  threads  already  cut.  It  can  also 
be  used  for  grinding  flat  drills  to  60°  for 
centre  drilling  of  lathe  work. 

A  screw  thread  gauge  of  circular  form  is  shown  in  Fig.  431, 
notched  to  suit  United  States  standard  threads.  The  single  large 


TOOLS. 


318 

V  is  for  grinding  the  tools,  while  all  the  other  spaces  are  formed 
correctly  to  the  size  of  thread,  so  that  they  may  be  used  for  testing 
the  accuracy  of  the  same.  The  type  is  also  made  for  Whitworth 
threads. 


Fig.  432. 


f'ig-  433- 


Fig.  434- 


Gauges  for  Acme  standard  threads,  to  take  the  place  of  square 
threads,  are  illustrated  in  Figs.  432  and  433,  and  having  angles  of 
14!°,  or  29°  included  angle.  The  idea  is  to  substitute  these  for 
square  threads  on  account  of  their  greater  strength,  and  also  to 

standardise  such  threads.  This,  it  will 
be  noted,  is  the  same  angle  as  that  which 
is  adopted  in  worm  threads  for  standard 
involute  cutters.  Another  gauge  is  used 
for  these  (Fig.  434),  giving  suitable  sec¬ 
tions  for  different  numbers  of  threads  per 
inch  of  the  worm. 

A  useful  form  is  that  with  a  number 
of  thin  pivoted  blades  at  each  end  of  a 
holder,  shut  up  like  a  pocket-knife  when 
not  in  use,  and  opened  out  when  re¬ 
quired.  They  contain  from  twenty-two 
to  twenty-six  blades,  each  one  being  ser¬ 
rated  at  the  edge  with  several  teeth  of 
one  pitch  of  screw.  The  blades  are  in 
some  cases  made  narrow  enough  to  enter 
into  nuts  and  similar  small  holes. 

The  changes  are  rung  on  the  screw  gauges  in  many  other 
ingenious  combinations.  One  is  shown  in  Fig.  435.  It  embodies 
the  standard  angles  for  tools  for  cutting  Whitworth,  and  Sellers 
threads;  two  right  angles  for  setting  square  objects,  one  being 


GA  UGES. 


319 

for  internal,  the  other  for  external  angles;  an  angle  of  120°  for 
testing  the  lips  of  twist  drills  by,  the  edge  being  divided  into 
millimetres  for  checking  the  length  of  the  lips;  an  angle  of  120° 
for  any  six-sided  object,  as  nuts ;  and  an  edge  divided  into  milli¬ 
metres  for  checking  the  pitches  of  screw  threads,  and  generally 
for  taking  small  measurements. 


A  special  gauge  is  Wyke’s  Universal  (Fig.  436).  It  has,  in 
addition  to  the  standard  vees,  an  adjustable  bevel  fitted  to  a  slot 
in  the  blade,  by  which  its  utilities  are  immensely  increased  in 
testing  angles  and  depths,  and  in  setting  tools  to  exact  angles. 
The  movable  blade  can  be  adjusted  in  any  position  and  clamped 
with  the  knurled  nut.  The  line  seen  on  the  face  of  the  main 


Fig.  437.  Fig.  438. 


stock  is  to  set  the  bottom  edge  of  the  blade  by,  thereby  provid¬ 
ing  an  angle  of  120°  between  the  graduated  edge  of  the  stock  and 
the  undivided  edge  of  the  blade.  Any  other  angles  can  be 
obtained  by  the  swivelling  of  the  small  blade,  rendering  the  tool 
of  wide  application,  either  in  machine  work  or  in  fitting,  to  which 
it  is  equally  adaptable. 

Figs.  437  and  438  represent  useful  combinations.  Fig.  437 


320 


TOOLS. 


combines  a  2  in.  rule  divided  into  sixteenths,  thirty-seconds,  and 
sixty-fourths,  right  angles,  an  angle  of  120°  for  nuts  and  drill 
points,  angles  for  screw  cutting,  and  a  few  holes  for  drills.  Fig. 
438  gives  a  3  in.  rule  finely  divided  (partly  shown  in  the  figure), 
notches  for  grinding  tools  for  cutting  square  threads,  angles  for 
vee  thread  tools,  and  some  drill  holes  from  one-sixteenth  to  one- 
fourth  of  an  inch. 


Circular  screw  thread  gauges  are  shown  in  Figs.  439  and  440. 
The  plug.  Fig.  440,  has,  in  addition  to  the  thread,  a  plain  end 
which  gives  the  size  of  the  tapping  hole.  The  internal  gauge. 
Fig.  439,  is  split  to  permit  of  closing  in  with  wear.  One  screw 
forces  the  halves  apart,  the  other  pulls  them  together.  The 
smooth  pins  help  to  prevent  lateral  spring,  which  is  likely  to  be 
caused  by  the  turning  of  the  screws,  and  which  would  spoil  the 


Fig.  440. 

accuracy  of  the  gauge.  This  type  is  made  by  the  Pratt  & 
Whitney  Company  in  two  styles.  Both  are  hardened  in  the 
angles  of  the  threads,  but  one  is  ground  subsequently ;  the  other 
is  not,  with  of  course  a  considerable  difference  in  price.  This 
gauge  represents  an  advanced  stage  in  construction,  since  for 
much  work  a  plain  solid  gauge  is  used  for  testing  finished  screws, 
being  either  in  the  form  of  a  flat  plate  with  a  screw  hole  in  it,  or 
formed  as  a  plug  of  circular  shape.  This  type  of  course  becomes 
unreliable  through  wear,  and  is  at  a  disadvantage  compared  with 


GAUGES. 


321 


that  in  Fig.  439,  in  which  very  delicate  adjustments  can  be  effected 
— either  closing  the  gauge  in  or  opening  it  out.  This  is  useful 
not  only  for  compensating  for  wear,  but  for  adjusting  to  suit  a 
particular  fit  of  thread,  either  easy  or  tight.  These  gauges  are 
used  largely  in  connection  with  screw  machine  work  for  testing 
the  finished  products,  which  must  pass  the  gauge  trial  or  be 
rejected. 

Another  group  of  screw  gauges  is  used  for  reference  only ;  that 


Fig.  441. 

is,  as  standards  with  which  working  gauges  are  compared.  These 
are  not  hardened,  and  are  not  tried  directly,  but  dimensions  are 
taken  with  calipers  and  transferred.  A  single-thread  gauge  costs 
the  same  as  a  pair  of  standard  gauges  which  are  hardened  but  not 
ground. 

The  Pratt  &  Whitney  Company  make  a  series  of  gauges  for 
the  Briggs  United  States  standard  pipe  threads,  and  another  set 
unhardened  for  reference.  The  internal  gauges  in  these  are 


Fig.  442. 


plain  rings  with  knurled  outsides,  the  plug  solid,  with  knurled 
handle. 

Many  gauges  are  made  as  in  Fig.  441,  the  particular  example 
being  an  Austrian  one,  having  the  diameters  at  top  and  bottom  of 
the  thread  at  the  opposite  end  to  the  screw. 

Plain  gauges  are  made,  as  in  Fig.  442,  for  measuring  the  sizes 
of  bored  holes  before  screwing,  two  sizes  being  provided  in  one 
body.  Another  style,  either  for  holes  to  be  screwed  or  left  plain, 
is  shown  in  Fig.  443, ‘having  a  number  of  steps,  advancing  by 
small  parts  of  an  inch,  or  of  a  millimetre.  It  resembles  some 
standard  corrective  gauges  in  form,  but  is  for  direct  measurement. 


X 


322 


TOOLS. 


The  wedge  principle  is  embodied  in  a  gauge  for  measuring  the 
diameters  of  holes  in  nuts  and  washers  (Fig.  444).  One  edge 


FTirozD 


Fig.  443- 


Fig.  444. 


1 

I 

i 

Fig.  445- 


reads  to  i6thsand  32nds,  the  other  to  loths  and  2oths  of  an  inch. 
As  a  single  gauge  of  this  kind  will  not  cover  a  large  range  of  holes, 

a  French  firm  makes  a  series  of  five, 
strung  on  a  ring,  the  series  covering 
all  dimensions  from  o  to  50  mm. 

Standard  tapers  have  their  gauges, 
both  internal  and  external,  as  showm 
in  Fig.  445,  both  being  knurled  on 
their  outsides. 

Keyways  are  tested  with  standard 
gauges  of  flat  sheet  form.  Fig.  446 
shows  one  for  verifying  the  bore  and 
keyway  relatively  to  each  other,  the 
tool  being  held  on  a  knurled  handle, 
which  fits  several  of  the  gauges.  Fig. 
447  gives  the  width  and  depth  of  the  key  on  one  side,  and  the 
width  and  depth  of  the  keyway  in  the  shaft  on  the  opposite  side, 
while  a  smaller  piece  provides  the  means  of  measuring  the  width 
of  the  keyway  in  the  bore.  These  gauges  can  be  used  equally 


GAUGES. 


323 

well  for  setting  the  tools  to  correct  widths  and  depths,  and  for 
testing  the  finished  work. 

A  useful  form  of  gauge,  of  which  we  need  not  say  much,  is 
that  having  holes  for  standard  drills,  and  holes  for  tapping  drills 
in  combination.  These  are  made  in  circular  and  oblong  form, 
and  the  two  sets  of  holes  are  also  made  in  separate  discs,  which 


are  pivoted  together  so  as  to  fold  up  and  occupy  little  space.  This 
type  of  gauge  is  of  more  use  for  setting  flat  drills,  which  are  forged 
to  shape,  than  for  twist  and  fluted  drills,  which  are  ready  provided 
to  standard  diameters,  and  are  stamped  with  their  sizes,  so  that 
the  gauge  would  be  of  no  use  for  them,  except  in  the  event  of  the 
size  being  defaced,  when  the  gauge  is  useful  to  verify  the  diameter. 

The  size  of  rod  for  screwing  is  also  conveniently  measured  with 
such  gauges. 

Fig.  448  shows  a  twist  drill  gauge,  employed  for 
measuring  the  angle  of  the  point,  indicating  whether  the 
same  is  central,  by  the  divisions,  and  also  for  measur- 
ing  down  the  shank,  thus  showing  whether  the  grinding 
has  been  done  equally. 

Wire  gauges  occur  in  numerous  designs  which  are 
so  familiar  that  it  is  not  necessary  to  illustrate  them. 

The  commonest  is  the  disc,  because  it  happens  to  be  Fig.  448. 
very  convenient  for  putting  in  the  waistcoat  pocket. 

Oblong  forms  are  also  commonly  used.  In  each  of  these  the 
wire  is  inserted  in  a  slot.  In  one  form,  in  order  to  avoid  the  in¬ 
convenience  of  one  large  disc,  two  discs  of  holes  are  pivoted 
together,  to  be  closed  over  one  another  when  not  in  service. 
An  elliptical  form  of  this  type  is  also  used.  Another  gauge  is 
the  wedge  shape  (Fig.  449),  in  which  the  wire  is  passed  down  the 
angular  opening  until  it  comes  into  contact  with  both  sides,  at 
which  place  the  dimensions  or  number  are  read  off. 


324 


TOOLS. 


In  a  combination  design,  an  oblong  gauge  and  a  movable 
caliper  are  united  (Fig.  450).  The  standard  slots  are  arranged 
down  each  of  the  outer  edges  of  the  blade,  and  a  sliding 
tongue  is  movable  in  a  recess  down  the  centre,  in  which 
it  can  be  clamped.  The  tongue  carries  a  caliper  leg  on 
the  blade,  and  graduations  on  the  edge  of  the  tongue 
give  direct  readings  of  size  for  odd  sizes  of  stock. 

The  subject  of  these  gauges  is  still  in  England  in¬ 
volved  in  much  confusion.  Many  mechanics  have 
endeavoured  to  evolve  some  order  and  standardisation 
out  of  the  chaos  which  exists.  The  result  is  that  the 
employment  of  the  uncertain  B.W.G.  still  predominates. 

There  is  probably  no  system  of  measurement  which 
has  been  involved  in  more  inextricable  confusion  than 
that  by  means  of  wire  gauges,  so  that  it  is  necessary 
when  giving  large  orders,  not  only  to  specify  the  gauge 
to  be  used,  but  also  the  size  in  fractions  of  an  inch,  or 
the  weight.  If  the  dimensions  are  given  in  decimals, 
these,  thanks  to  the  micrometer  calipers,  are  very  easily 
checked,  and  it  also  eliminates  the  errors  due  to  the  use 
of  gauges  badly  worn. 

Mr  Latimer  Clark  once  gave,  by  way  of  illustration  of 
the  uncertainty  attendant  on  the  use  of  these  gauges,  the 
case  of  a  specification  for  a  contract  which  he  had  occa¬ 
sion  to  prepare,  in  which  the  use  of  either  one  or  other 
of  two  gauges  would  have  made  a  difference  of  ^8,000 !  The 


A 

_i- 

.33 

j« 

18. 

J7 

18. 

.18 

20. 

2J- 

2?_ 

_*1 

23- 

-2Z 

2+- 

-23 

£3. 

-20- 

26- 

27- 

-rn — 

j 

.27 

.28 

C 

Fig.  449 

n  u  u  i  A  rinmrrimnnnr~ 

l1  1  1  i  1 

L  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1 

J“TJT_riJTJlJTJ-U^ 

Fig.  450. 

B.W.G.  is  the  parent  of  the  others  in  the  sense  of  priority  of 
age,  its  origin  being  lost.  A  gauge  bearing  date  1795  is,  or 


GAUGES. 


325 


was,  recently  in  existence,  while  Mr  Hughes  has  shown  that 
the  ordinary  numbers  of  wire  were  in  use  in  1735,  earlier. 
It  appears  to  have  originated  in  the  requirements  of  the  wire- 
workers  themselves,  and  to  have  been  constructed  in  a  purely 
empirical  manner.  Originally  employed  for  iron  wire  only,  it 
was  called  the  Birmingham  iron-wire  gauge ;  subsequently  it 
has  been  used  indiscriminately  for  brass,  copper,  black  steel 
wire,  sheet  iron  and  steel,  and  for  screws.  Originally  its  di¬ 
mensions  are  thought  to  have  been  given  in  32nds  and  bqths, 
though  now  stated  in  thousandths  of  an  inch,  or  “  mils.”  Mr 
Latimer  Clark  believed  the  gauge  to  have  originated  by  calling  the 
largest  wire  which  could  be  drawn  in  the  days  of  hand  labour 
No.  I,  and  the  next  smaller  size  which  could  be  drawn  at  one 
operation  No.  2,  and  so  on ;  so  that  the  various  sizes  would  be 
determined  by  the  power  of  the  hand  appliances  then  available  for 
drawing  on  the  one  hand,  and  the  cohesive  strength  of  the 
materials  on  the  other. 

In  the  report  made  to  the  Council  of  the  Society  of  Telegraph 
Engineers  in  1879  it  was  stated  that  the  different  gauges  in 
use  could  be  counted  by  hundreds ;  that  every  wiredrawer  had 
gauges  made  to  suit  special  objects ;  that  owing  to  keen  compe¬ 
tition,  wire  was  drawn  by  one  gauge  and  sold  by  another  ;  that  half 
and  quarter  sizes  were  sold  as  whole  sizes,  workmen  being  paid  by 
one  gauge  and  the  wire  sold  by  another ;  and  that  as  many  as 
seven  different  gauges  had  been  made  between  20  and  21,  and 
also  that  the  sheet  gauges  proper  were  no  less  unreliable  than  the 
wire  gauges.  A  considerable  amount  of  discussion  resulted ; 
various  new  gauges  were  proposed,  based  on  geometrical  principles, 
and  ultimately  the  Board  of  Trade  sanctioned  the  “New  Imperial 
Standard  Wire  Gauge,”  the  highest  size  of  which,  70,  is  |  in.  in 
diameter,  and  the  lowest,  50,  is  one  mil.  Even  this 

has  not  met  with  general  acceptance,  for  the  old  B.W.G.  holds 
its  own,  and  will  do  so  probably  for  a  generation  or  two  longer,  as 
do  the  English  measures  in  the  face  of  the  decimal  system.  The 
B.W.G.  is  used  in  England,  Germany,  America,  Canada,  and  to 
a  limited  extent  in  Russia  and  France.  As  usually  made,  the 
numbers  in  the  plate  run  from  i  to  26,  but  plates  are  also  made 
from  I  to  30,  I  to  36,  I  to  40,  and  18  to  40.  For  certain  wires — 
pianoforte,  &c. — special  gauges  are  used. 

The  United  States  have  a  standard  gauge  for  sheet  and  plate 


326 


TOOLS. 


iron  and  steel,  the  use  of  which  is  compulsory  by  an  Act  of  the 
Senate  which  has  been  in  force  since  1893,  other  is  per¬ 

mitted  to  be  employed.  It  embraces  thicknesses  ranging  from  \  to 
in.,  denoted  by  forty-five  consecutive  numbers.  Brown  & 
Sharpe  have  a  wire  and  sheet-metal  gauge,  which  has  been  adopted 
by  the  brass  manufacturers.  It  gives  a  grade  of  sizes  which  range 
in  geometrical  progression,  instead  of  by  irregular  increments,  as 
does  the  B.W.G. 


CHAPTER  XXVIIL 


Indicators  and  Templeting. 

Principle  of  Design — Examples — Relation  to  the  Surface  Gauges — Templeting 
—Templets  and  Jigs— Their  Preparation— Weight— Stamping— Metric 
System. 

INDICATORS  are  filling  a  larger  place  in  the  workshop  than 
they  did  formerly.  The  principle  which  underlies  their  design 
is  the  magnification  of  slight  errors  which,  though  scarcely 
visible  if  measured  directly,  are  rendered  very  apparent  by  being 
magnified  at  the  end  of  a  long  lever.  Although  the  principle  is 
simple,  many  refinements  are  introduced  into  different  forms. 
There  are  two  classes,  one  for  lathe  work  specially,  another  for 
testing  work  during  machining  and  in  course  of  erection. 

One  of  the  simplest  types,  the  Brown  &  Sharpe,  Fig.  451,  is 


fitted  by  a  universal  joint  to  one  end  of  a  rectangular  bar  a,  made 
of  a  suitable  section  to  be  held  in  the  toolpost  of  a  lathe.  When 
a  vertical  movement  only  is  wanted,  the  indicator  can  be  clamped 
so  that  the  bar  or  finger  will  only  move  vertically  in  its  joint.  The 
bushing  that  holds  the  finger  is  split  so  that  the  latter  can  be  slid 
lengthwise.  A  spiral  spring  exercises  an  even  pressure  on  the 
fingers,  two  of  which  are  fitted,  one  with  a  centre  having  60°  of 
angle,  the  other  with  a  turned-up  point. 

An  indicator  of  another  type  by  the  same  firm  is  shown  in  Fig. 


3^8 


TOOLS. 


452.  It  is  used  for  testing  other  work  besides  that  done  in  the 
lathe,  such  as  in  the  erecting  or  testing  of  machinery.  It  has  a 


Fig.  452. 


base,  a  post,  and  an  arm,  carrying  the  actual  indicating  rod.  The 
base  is  of  girder  form.  The  post  can  be  slid  along  it  and 


clamped  in  any  position  by  a  thumb  nut,  and  the  sleeve  which 
carries  the  arm  can  be  secured  at  any  height  on  the  post.  The 
arm  can  be  turned  in  its  sleeve  and  set  at  any  vertical  angle  to 


INDICATORS  AND  TEMPLETING.  329 

bring  the  point  downwards  or  upwards,  or  it  can  be  removed 
and  used  apart  from  the  post.  An  index  finger  at  the  opposite 
end  of  the  pointer  moves  over  graduations  of  thousandths 
of  an  inch,  and  so  multiplies  the  movements  of  the  point.  It 
can  be  used  in  the  lathe,  as  well  as  on  surface  work. 

The  Starrett  universal  indicator.  Fig.  453,  is  mounted  on  a 
heavy  base  a,  which  can  be  clamped  in  the  toolpost  of  a  lathe  or 


elsewhere,  or  slid  along  surfaces,  in  scribing  block  fashion.  It  is 
adapted  for  face  work,  or  for  inside  or  outside  surfaces  against 
which  the  flats  on  the  head  at  the  extreme  left  hand  b,  b  in  the 
figure  are  set.  These  points  are  equidistant  from  the  fulcrum. 
The  needle  is  kept  normally  at  zero  by  the  operation  of  a  spring 
which  has  to  be  reversed  when  the  head  is  used  above  and  below 
the  work  respectively.  The  change  is  effected  by  turning  the  disc 


Fig.  455- 


Fig.  456. 


slightly  to  which  the  spring  is  attached.  The  indicator  reads  to 
thousands  of  an  inch.  The  instrument  can  be  clamped  to  a 
support  other  than  the  base,  as  to  the  needle  of  a  surface  gauge. 

The  Bath  indicator.  Figs.  454  to  456,  is  a  rather  elaborate  bit 
of  mechanism,  comprising  a  series  of  compound  levers  enclosed  in 
a  case  (see  Fig.  454),  by  which  the  movement  of  the  feelers,  one 
of  which  is  seen  at  a,  is  multiplied,  b  is  the  needle  reading  over 
the  graduated  scale.  It  is  kept  normally  in  its  zero  position  by  the 


33° 


TOOLS. 


spring  c.  The  feelers  are  tapped  into  the  hinged  block  d,  four 
being  fitted  alternatively  to  suit  various  classes  of  work,  the  one 
shown  in  Fig.  456  being  for  testing  holes.  Fig.  455  is  a  plunger 
that  goes  between  lathe  centres  to  test  the  truth  of  work  being 
chucked  by  a  hole.  One  end,  the  pointed  one,  fits  in  a  hole  or 
centre  in  the  work ;  the  other  slips  over  the  poppet  centre.  One 
of  the  feelers  is  then  brought  up  against  the  outside  of  the  plunger, 
and  its  readings  indicate  by  how  much  it  runs  out  of  truth,  and  of 
course  the  hole  in  the  work  also. 

There  is  some  resemblance  between  the  surface  gauges  and  the 
indicators.  The  important  difference  is  that  the  first-named  do 
not  show  by  readings  how  much  work  is  out,  while  the  indicator 
does.  The  indicator  is  used  for  many  purposes  for  which  in 
average  practice  the  surface  gauge  has  been  and  is  used.  It  is,  for 
example,  employed  for  levelling  work  on  the  planer  and  during 
course  of  erection.  It  also  takes  the  place  of  the  scriber  in  testing 
work  on  the  faceplate  and  between  centres ;  or,  to  go  into  rougher 
classes  of  testing,  it  supersedes  the  chalk  marks  put  on  rotating  work 
to  test  the  amount  of  eccentricity.  It  also  tests  the  truth  of  vertical 
faces,  holding  the  bar  of  the  instrument  in  a  toolbox  or  other  fixed 
support,  and  traversing  the  face  in  relation  to  it.  In  the  hands  of 
some  men  the  indicator  is  a  most  valuable  instrument  for  precision 
measurements.  It  is  especially  useful  to  machine-tool  makers. 
Machines  when  set  up  may  be  tried  for  their  limits  of  inaccuracy, 
such  as  in  parallelism  of  spindles  and  slides,  the  indicator  giving 
the  most  delicate  shades  of  difference,  or  taper.  Readjustments 
may  then  be  made  until  the  indicator  shows  that  the  work  is 
correct. 

We  conclude  the  present  subject  with  a  brief  explanation  of 
the  methods  of  templeting.  This  system  is  adopted  in  order  to 
avoid  the  necessity  of  marking  out  every  separate  piece  of  work. 
A  templet  being  made,  every  similar  piece  is  marked  directly  from 
that,  without  any  aid  from  measuring  instruments.  The  classes  of 
jobs  to  which  this  method  is  applied  are  practically  illimitable, 
ranging  from  those  of  small  dimensions  to  very  big  framings.  Such 
templets  may  include  provisions  for  several  sets  of  operations  on 
one,  or  on  more  than  one,  plane.  They  serve  to  line  out  work  for 
planing  and  shaping,  and  for  drilling  and  boring,  and  they  serve 
to  mark  angular  relations  as  well  as  lines  on  surfaces. 

Another  class  of  templets  is  that  to  which  the  term  jigs  is  com- 


INDICATORS  AND  TEMPLE  TING. 


331 


monly  applied.  The  distinction  between  the  two  is  that  the  first- 
named  are  used  for  marking  out  by;  the  second  are  for  machining 
by,  without  preliminary  marking  out. 

In  the  first  system,  measurement  cannot  be  dispensed  with  for 
the  purpose  of  checking  the  work  as  it  proceeds ;  in  the  second  it 
is  seldom  necessary,  unless  it  takes  the  form  of  gauging.  The 
difference  is  that  error  may  arise  in  working  by  scribed  lines  ;  but 
when  the  tools  are  controlled  by  a  jig,  little  or  no  error  can  creep 
in,  neither  can  the  coercion  of  the  jig  be  avoided.  If  the  jig  is 
incorrect  it  must  be  altered  or  another  made. 

Both  templets  and  jigs  are  made  of  sheet  metals,  or  castings, 
the  difference  depending  mainly  on  what  they  have  to  do.  Tem¬ 
plets  for  marking  out  only  are  generally  of  sheet  metal,  filed  to  the 
outlines  of  the  work  to  be  marked  therefrom,  and  having  any  holes 
required  drilled  or  cut  in  them.  Centre  lines  are  frequently  used 
for  setting  them  by.  In  other  cases,  commencement  is  made  from 
an  edge  or  edges.  Templets  save  a  great  deal  of  trouble  in  the 
tentative  markings-out  that  are  so  often  employed  to  ensure  that 
all  portions  shall  hold  up  for  tooling. 

In  some  shops  the  templet  markers  work  by  themselves,  doing 
little  or  nothing  else.  In  many  the  fitters  make  their  own  templets. 
The  usual  plan  is  to  build  one  machine,  or  engine,  first,  and  then, 
taking  it  apart,  prepare  the  templets  of  the  several  portions.  This 
is  the  safe  way.  If  the  attempt  is  made  to  prepare  templets  for 
sets  of  work  from  the  drawings,  error  is  almost  sure  to  arise  except 
in  the  simplest  sections,  or  in  those  where  certain  hard-and-fast 
dimensions  must  be  observed. 

The  making  of  most  jigs  involves  more  scheming  than  that  of  tem¬ 
plets.  These  have  acquired  a  greater  prominence  in  modern  shops 
than  they  did  in  the  older  ones.  In  the  majority  of  cases  they  are 
used  for  locating  the  centres  of  holes,  the  drills  or  reamers  being 
controlled  by  the  holes  in  the  jigs.  In  most  cases  wear  is  delayed 
as  long  as  possible  by  using  bushings  for  the  holes,  made  of 
hardened  steel.  They  may  be  replaced  with  new  ones  as  they  wear 
badly,  without  affecting  the  relative  position  of  the  holes.  In  many 
instances  bushings  are  essential,  as  where  the  main  body  of  the  jig 
is  made  of  sheet  metal,  and  the  bushings  are  required  thicker  than 
this.  But  when  the  frame  of  the  jig  is  of  cast  iron,  hardened  steel 
bushes  are  essential,  otherwise  the  holes  in  the  cast  iron  would 
wear  rapidly  by  the  friction  of  the  body  of  the  drill. 


332 


TOOLS. 


An  important  matter  to  consider  is  the  lessening  of  weight  in 
templets  and  jigs.  Thus,  though  those  of  small  dimensions  are 
frequently  made  in  cast  iron,  large  ones  are  properly  plated,  often 
being  built  up  of  several  strips  united  with  light  angles.  A  solid 
sheet  of  metal  is  not  necessary  or  desirable  in  large  templets  and 
jigs.  The  only  essential  parts  are  the  working  portions,  and  it  is 
sufficient  if  these  are  tied  together  suitably  with  narrow  strips. 
Though  in  the  case  of  small  holes  steel  bushings  are  used,  yet  in 
large  bearing  holes  that  have  to  be  bored,  castings  are  often  bolted 
or  riveted  at  those  places  to  the  sheet  metal. 

It  is  necessary  to  stamp  all  templets  and  jigs  with  full  particulars 
of  the  job  for  which  they  are  made,  as  the  order  number,  the  date, 
and  the  piece.  If  more  details  are  wanted  they  can  be  tabulated 
in  a  book. 

In  conclusion,  in  the  matter  of  measurement,  as  in  some  other 
departments  of  engineering  practice,  we  cannot  help  observing  how 
the  practice  of  the  shops  is  undergoing  change.  Old  methods  sur¬ 
vive,  and  must  do  so,  but  they  become  more  deeply  invaded  by 
the  new.  It  is  not  that  the  fitting  of  parts  is  more  precise  than 
was  possible  of  old,  but  that  now  it  is  both  precise  and  positive, 
while  the  old  was  exact  only.  This  is  the  result  of  the  invasion  of 
the  gauges.  Their  two  great  subdivisions,  fixed  and  micrometric, 
render  the  taking  and  checking  of  the  finest  measurements  practic¬ 
able  and  easy — so  easy,  in  fact,  that  the  gaugers  in  shops  are  not 
skilled  hands,  but  lads  and  girls.  The  rivalry  of  the  old  and  the 
new  is  only  limited  by  the  extent  to  which  high  specialisation  will 
take  the  place  of  the  general  shops. 

A  related  question  that  has  been  much  discussed  recently  is 
the  compulsory  introduction  of  the  metric  system.  Actually  we 
have  seen  that  most  of  the  measuring  tools  are  made  to  metric 
measures,  as  well  as  to  duodecimal.  This  testifies  to  the  inroad 
which  the  former  has  made  in  our  shops.  Neither  America  nor 
England  has  adopted  the  metric  measures,  and  yet  nearly  every 
class  of  instrument,  rules,  and  gauges  that  we  have  described 
are  offered  in  both  systems,  either  on  the  same  tool  or  separate 
ones.  And  these  are  not  nearly  so  much  for  foreign  use 
as  for  home.  German  and  French  firms  are  quite  able 
to  supply  their  own  people,  and  are  practically  independent  of 
American  and  English  goods.  Machinists  therefore  would  have 
nothing  to  lose  by  the  change  to  the  metric  system — in  fact,  they 


INDICATORS  AND  TEMPLETING. 


333 


have  to  work  by  it  in  executing  a  good  many  orders.  Already,  too, 
in  our  finest  measurements  we  think  decimally,  if  not  in  fractions 
of  the  metre,  in  those  of  the  inch.  Tenths,  hundredths,  thou¬ 
sandths,  &c.,  have  already  practically  displaced  the  sixteenths, 
sixty-fourths,  and  the  broken  vulgar  fractions,  in  good  machine 
work.  Now  most  men  have  to  use  two  sets  of  measuring  instru¬ 
ments,  while  under  the  decimal  system  one  would  suffice.  Already 
some  leading  firms  have  adopted  it,  and  others  will  follow,  so  that 
long  before  the  system  is  legalised  it  will  probably  be  in  active  use 
in  all  the  leading  works. 


INDEX. 


Abrasion,  i8 

Abuse  of  rules,  226 
Accuracy,  its  limitations,  217,  218 
—  of  gauges,  limits  of,  31 1,  312 
Adze,  26,  31,  32 
Angle,  and  edge,  22 
—  board,  48 

—  cutting,  of  chisels,  24,  25 
—  of  clearance,  front  rake,  or  relief,  8, 
12 

—  of  top  rake,  8,  1 1 

Angles  of  cutting  tools,  6,  8,  24 

—  of  drills,  128,  129,  130,  133,  136 

—  of  lathe  tools,  210 

—  of  plane  irons,  42 

—  of  screw  threads,  153 

Annealing  tools,  186 

Appliance,  definition  of,  2 

Arboring  tools,  77,  150 

Axes,  3D  32 

—  Paleolithic,  20 


Backing-off  of  taps,  154 

Baily’s  metal,  220 
Band  saws,  81,  82 
Beam  micrometers,  296 
Bent  gouges,  35 
Bevel  protractors,  240-243 
Bevels,  239,  240 
Bill  hook,  31 
Bits,  121-125 

Birmingham  wire  gauge,  325 
Blocks,  levelling,  251 
Boring  tools,  147,  148,  149 
—  tools  for  sheet  metal,  148 
—  tools  for  wood,  120-126 
Bossing  tools,  150 
Box  spanner,  172,  173 
—  tools,  16 
Braces,  173 
Brass  tools,  60,  62 


Bronze  chisels,  21 
—  standard  bars,  220 
Buckling  of  saws,  90 


CALIPER,  and  wire  gauge,  324 
—  compass,  277 
—  gear  teeth,  299 
—  key  way,  277 
—  rules,  226,  279 
—  vernier,  281-286,  291 
Calipers,  271-299 
—  essentials  in,  271,  272 
—  fine  adjustments  of,  273,  274,  279, 
281,  287,  291 
—  horseshoe^  309 
—  loose  measuring  points  of,  294 
—  micrometer,  287-298 
—  micrometer,  double,  295 
—  micrometer,  screw-thread,  298,  299 
—  to  use,  274,  275,  276,  277 
—  wear  of,  290,  291-293 
—  with  compass  points,  284,  285 
Cape  chisel,  54,  56 
Care  of  planes,  51,  52,  53 
Carvers’  chisels,  33 
—  gouges,  35 

—  tools,  handles  of,  177,  178 
Caulking  tools,  166,  167 
Celts,  Neolithic,  20 
Centre-bit,  122 
—  popping,  251 

—  punch  for  test  pieces,  307,  308 

—  square,  238 

Chatter  of  planes,  40 

Chipping,  55,  56 

Chisel  as  a  splitting  tool,  23 

—  cape,  54,  56 

—  cold,  54,  55  _ 

—  compared  with  plane  iron,  13,  38,  43 
—  cow-mouth,  54,  56 
—  cross-cut,  54,  56 


INDEX. 


Chisel,  diamond  point,  54,  56 

—  for  wood  turning,  33,  34 

—  handles,  178,  179 

—  method  of  use,  27,  28,  29,  32,  33 

—  round  nose,  54,  36,  76 

—  setts,  54,  56,  57 

—  woodworkers’,  7,  9,  21,  76 
Chisels  actuated  by  pressure,  24,  26 

—  carvers’,  33 

—  coachmakers’,  25 

—  driven  by  mallet,  29 

—  firmer,  25-28 

—  for  metal  working,  54-57 

—  for  wood  turners,  24,  26 

—  guidance  of,  32,  38 

—  mortise,  25,  29,  30 

—  paring,  24,  28,  29 

—  rigidity  of,  25 

—  used  percussively,  22 
Choppers,  31 

Chords,  scale  of,  242,  243 

Circular  saws,  81,  82 

Clearance,  front,  8,  12 

Clearances  of  drills,  133,  134,  135,  136 

Coachmakers’  chisels,  25 

Cold  chisel,  54,  55 

Combination  calipers,  and  gauge,  324 

—  compasses,  266,  267 

—  forms  of  screw  thread  gauges,  318, 

319 

—  squares,  238,  239 
Compass  caliper,  277 

—  points  to  calipers,  284,  285 
Compasses  and  dividers,  263-267 

—  combination,  266,  267 
Correction  of  squares,  235 
Counterbores,  150 
Counterboring  in  wood,  125 
Cow-mouth  chisel,  54,  56 
Cramps,  176 

Cranked  tools,  58,  59,  60 
Cross-cut  chisel,  54,  56 
■ — ■  saws,  80 
Cut  of  files,  96 
Cutter  grinding,  2U,  212 

—  grinding  machine,  213,  214 
Cutting  angle  of  chisels,  24,  25 

—  angle  of  plane  irons,  42 

—  edges  of  drills,  130,  131,  132 
Curves  of  gouges,  35,  36 
Cylinder,  lining  out  of,  249 


D-bits,  149 

Depth  gauges,  300-305 
Diamond  point  chisel,  54,  56,  76 
Dies  and  taps,  action  of,  151,  152,  153 


335 

Dies,  cutting  threads  of  opposite  hand, 

159 

—  operation  of,  155,  156,  157 

—  used  in  screw  machines,  158 
Dividers  and  compasses,  263-267 

—  parallel,  270 

—  wear  of  thread,  265 
Drawing  temper,  185 
Draw  knife,  33 

Dressers  for  emery  wheels,  195 

Drifts,  57,  163 

Drill  gauges,  319,  323 

—  notched,  143 

—  points,  136 

—  rock,  32 

Drills,  angles  of,  128,  129,  133,  136 

—  as  cutting  tools,  130,  13 1 

—  clearances  of,  133,  134,  135,  136 

—  lubrication  of,  139,  140,  141 

—  running  out,  130 

—  slot,  142,  143 

—  speeds  of,  137,  138,  139 

—  symmetry  of  edges,  129,  130 

—  twist,  13 1 


Early  measurements,  218 
Ech oil’s  taps,  158,  159 
Edge,  keenness  of,  22 
—  mills,  103,  104,  105,  108 
Emery  wheel  dressers,  195 
—  wheels  compared  with  grindstones, 

193,  194 

—  wheels,  forms  of,  195,  212 
—  wheels,  grades  of,  194 
—  wheels,  speeds  of,  194 
—  wheels,  truing  of,  195 
End  mills,  103,  104,  105 
Expanding  centre-bit,  123 
—  reamers,  145,  146 


Face  mining,  112 

—  mills,  112-114 
Eacing  tools,  150 
Feeds  of  planer  tools,  64 
—  of  slotting  tools,  65 
File  handles,  177,  178 
Files,  93-97 
—  cut  of,  96 
—  for  saws,  87,  88 
—  longitudinal,  fo-ms  of,  95 
—  sections  of,  94 
Filing  saws,  87,  89 
Finishing  tools,  59,  60,  64 
Firmer  chisels,  25,  28 
—  gouges,  34,  35 


336 


INDEX. 


Flat  bit,  149 
Flatter,  168 

Flexure  of  standard  bars,  221 
Fluted  reaineis,  146,  147 
Formative  tools,  170 
Formed  milling  cutters,  118 
Former  for  milling,  112 
Forming  tools  for  brass  work,  71 
Forms  of  files,  longitudinal,  95 
Fullering  tools,  169 


Gang  mills,  105, 106, 107, 108 
—  planer  tool,  65 
Gas  pliers,  175 
Gauge  fits,  310 
—  height,  303,  304 
—  long  tooth,  307 
—  mortise,  307 
—  spacing,  307,  308 
—  for  twist  drills,  323 
Gauges,  depth,  300-305 
—  for  drills,  319,  323 
—  for  keyways,  322,  323 
—  for  screw  threads,  317 
—  for  standard  tapers,  322 
—  for  tapping  holes,  320,  321 
—  for  woodworkers,  307 
—  limits  of  accuracy,  31  r,  312 
—  limits  of  tolerance  in,  310,  313 
—  micrometer  rod,  306 
—  plug  and  ring,  312 
—  ring,  versus  fixed  calipers,  31 1 
—  rod,  301,  305-307 
—  screw  thread,  combination  forms, 
318,  319 

—  snap,  309,  3 1 2-3 1 5 
—  surface,  247-261 
—  testing,  316 
—  versus  rules,  215,  216 
—  wear  of,  31 1,  315,  316 
—  wedge,  322 
—  wire,  323-326 
Gear  teeth  caliper,  299 
Gimlet,  120 
Gouge  setts,  56,  57 
—  slips,  202 
Gouges,  34 
—  bent,  35 
—  carver’s,  35 
—  curves  of,  35,  36 
—  driven  by  mallet,  34,  36 
—  firmer,  34,  35 
—  grinding  of,  200 
—  paring,  34 
—  turning,  36,  37 
Grinders  for  tools,  195-209 


Grinding  cutters,  211,  212 

—  gouges,  203 

—  plane  irons,  199 

—  precision,  202,  203 

—  tools,  187,  188,  189 

—  wet,  195 

—  wheels,  forms  of,  212 
Grindstone,  action  of,  193 

—  mounting,  192 

—  treatment  of,  193 
— -  truing,  19 1 

— -  water  on,  193 
Grindstones,  189,  190 

—  compared  with  emery  wheels,  193, 

194 

—  speed  of,  192 
Guidance  of  planes,  44,  48 
Guide  screw  stock,  157 
Gulleting  saws,  90 


Hammers,  163-165 

Handles,  materials  used  for, 
180 

—  of  carver’s  tools,  177,  178 
—  of  chisels,  178,  179 
—  of  planes,  179,  180 
—  of  saws,  179,  180 
—  of  tools,  177-181 
—  of  turning  tools,  179 
Hand-saw,  79 

Hardening  and  tempering,  182-186 

—  tools,  182,  183,  184,  185 

Hatchets,  31 

Height  gauge,  303,  304 

High  speed  drills,  139 

—  speed  steels,  5 

Hob.  155 

Hollow  and  round  planes,  45,  46 
Hones,  200,  201,  202 
Horseshoe  calipers,  309 


INCREASING  twist,  132 
1  Indicators,  327-330 
Inserted  tooth  mills,  113,  114,  115, 
1 16. 

Inside  gouges,  34 
—  tools,  60 

Instruments,  definition  of,  2 
Interchangeability,  218,  310 
Interchangeable  system,  3,  4,  5 
Iron  planes,  13,  42,  47 


JIGS,  331,  332 

Joints  in  milling  cutters,  106,  107 


INDEX. 


337 


Keyway  calipers,  277 
—  gauges,  322,  323 
Knife  tools,  i6 


Land,  133 

Lath  render,  31 
Leather  strop,  201 
Levelling  blocks,  251 
—  with  scribing  block,  252,  253,  254 
Levels,  243-246 
Limit  of  tolerance,  310,  313 
Lining  out  work,  247-251,  278 
Long-tooth  gauge,  307 
Lubrication  assists  cutting,  17 
—  of  drills,  139,  140,  141 
—  of  milling  cutters,  116,  117,  118, 
119 


Mallet  driving  for  chisels,  29 
—  driving  for  gouges,  34,  36 
Mallets,  165,  166 
Marking-off  table,  250 
Materials  control  tool  angles,  15 
Measurement,  216 
—  definition  of,  215 
—  effects  of  temperature  on,  217 
—  standards  of,  218-224 
—  early,  218 
Measuring  machine,  287 
Metal  facing  tools,  77 
Metre,  219 

Metric  system,  332,  333 
Micrometer,  280,  281 
—  calipers,  287-298 
—  calipers,  beam,  296 
—  calipers,  double,  295 
—  calipers,  screw  thread,  298,  299 
—  depth  gauges,  302 
—  readings,  290 
—  rod  gauges,  306 
Micrometric  surface  gauges,  260,  261 
Milling  by  former,  112 
—  cutters,  98-119 
—  cutters,  angular,  109 
—  cutters,  conditions  which  govern 
efficiency,  99,  100,  loi,  102 
—  cutters,  edge,  103,  104,  105,  108 
—  cutters,  end,  103,  104,  105 
—  cutters,  jointing  of,  106,  107 
—  cutters,  lubrication  of,  116,  117,  118, 
119 

—  cutters,  profilled,  109,  no 
—  cutters,  shearing  action  of,  71,  99, 
100,  loi,  102 


Milling  cutters,  speeds  of,  100,  loi 

—  cutters,  with  formed  teeth,  118 

—  face,  1 12 

—  profilled,  no,  nr,  112 
Mills,  face,  112,  113,  114 

—  with  inserted  teeth,  113,  114,  115, 

116 

—  with  staggered  teeth,  73,  117 
Mitre  board,  48 

Monkey,  164,  165 
Morse  tapers,  142 
Mortise  chisels,  25,  29,  30 

—  gauge,  307 
Moulders’  tools,  170,  171 
Moulding  tools,  168-171 

—  planes,  45,  46,  52 
Mounting  grindstones,  192 


Natural  grindstones,  189,  190 
Nicking,  effect  of,  169,  170 
Notched  drill,  143 


OIL  slips,  202 

Oilstones,  200,  201,  202 
Outside  gouges,  34 


PARING  chisels,  24,  28,  29 
—  gouges,  34 
Parting  tools,  59,  60 
Pendulum,  219 

Percussion  exercised  on  chisels,  24 
Pincers,  175 
Plane,  choking  of,  40 
—  handles,  179,  180 
—  iron  compared  with  chisel,  7,  38, 
43 

—  iron,  fastening  of,  39,  40 
—  iron,  rigidity  of,  40 
—  iron,  setting  of,  51 
—  top  iron  of,  ii,  13,  40,  41 
— •  irons,  angles  of,  42 
—  irons,  grinding  of,  199 
Planer  and  shaper  tools,  59,  60,  61-64 
—  and  shaper  tools,  speeds  of,  65 
Planes,  II,  38,  53 
—  care  of,  51,  52,  53 
• — •  chatter  of,  40 
—  iron,  13,  42,  47 
—  linear  guidance  of,  44,  48 
—  hollows  and  rounds,  45,  46 
—  methods  of  use,  47,  48,  49 
—  moulding,  45,  46,  52 
—  profiles  of,  45 
—  selection  of,  53 


INDEX. 


338 

Planes,  top  iron  of,  ii,  13 

—  rebate,  46,  47,  48 

—  rigidity  of,  43 

—  wear  and  tear,  7 
Planing  stuff  true,  49,  50 
Plates  of  saws,  82,  83 

—  surface,  231,  232 
Pliers,  175 

Plumb  bobs,  245,  246 

—  rule,  246 
Points  of  drills,  136 
Precision  grinding  of  tools,  202,  203 
Pressure  exercised  on  chisels,  24 
Profile  milling,  no.  III,  112 
Profiled  milling  cutters,  109,  no 
Profiles  of  planes,  45 
Protractors,  240-243 

Punched  burr,  162 
Punching  and  drilling,  162 
Punch,  spiral,  160 
Punches,  160,  162 

—  taper  of,  1 61 

—  various,  162 


q: 


UENCHING,  184,  185 


Rake,  front,  8,  12 
—  top,  8,  n 
—  side,  top,  56 
Ratchet  braces,  173 
Reamers,  expanding,  145,  146 
—  fluted,  146,  147 
—  solid,  144 

Rebate  planes,  46,  47,  48 
Reciprocating  saws,  81 
Relief,  angle  of,  8,  12 
—  of  taps,  154 
Right  and  left  hand  tools,  59 
Rigidity  of  planes,  43 
—  of  tools,  13 

Ring  gauges  versus  fixed  calipers,  311 
Rock  drill,  32 
Rod  gauges,  301,  305-307 
Roughing  tools  for  metal,  58,  59,  6l 
Round-nose  chisel,  54,  56,  76 
Router  plane,  39 
Rule  combined  with  square,  225 
Rules,  216,  224-227 
—  abuse  of,  226 
—  caliper,  279 
—  how  used,  226,  227 
—  rods,  standard,  229 
—  versus  gauges,  215,  216 


SAW  files,  87,  88 
—  filing,  87,  89 
—  hand,  79 
—  plates,  82,  83 
—  setting,  85,  86,  87 
—  teeth,  79,  80,  81 
—  teeth,  gulleting  of,  8 1 
—  teeth,  spacing  of,  8 1 
Sawing,  91,  92 
Saws,  78-92 
—  band,  81,  82 

—  both  chisels  and  scrapes,  78,  79 
—  buckling  of,  90 
—  circular,  81,  82 
—  cross  cut,  80 
—  gulleting  of,  90 
—  handles  of,  179,  180 
—  reciprocating,  81 
—  set  of,  84,  85 
—  speeds  of,  82 
—  topping,  87 
—  types  of,  81 
Scale  of  chords,  242,  243 
Scales,  227,  228 

Scrape  for  wood  and  metal,  76,  77 

Scrapes,  18,  75,  76,  77 

Scraping  action,  18,  75,  76,  77 

—  tools,  75-77,  93 

Screwdrivers,  177 

Screw  thread  gauges,  317 

—  thread  micrometer  calipers,  298,  299 

—  thread,  tools,  6 1 

—  threads,  angles  of,  1 53 

Scriber,  261,  262 

—  blocks,  247-261 

—  blocks,  levelling  with,  252,  253, 

254 

—  blocks,  locating  centres  with,  254 

Sections  of  files,  94 

Sellers’  tool  grinder,  202-209 

Set  of  saws,  84,  85 

—  squares,  238,  239 

Setting  of  saws,  85,  86,  87 

Setts,  54,  56,  57 

Shaper  and  planer  tools,  speeds  of,  65 
Sharpening  tools,  200,  201,  202 
Shavings  and  chips,  lO,  1 1,  12 
Shear  blades,  72 
Shearing,  18,  67-74 
—  action  in  forming  tools,  71 
—  action  in  milling  cutters,  71,  99 
—  action  in  planer  tools,  71 
—  tools,  69-74 
Shooting  board,  48 
Slot  drills,  142,  143 
Slotting  machine,  tools  for,  66-68 
Smiths’  flatter,  168 


INDEX. 


339 


Smiths’  moulding  p  ocesses,  170 
Snap  gauges,  309,  312-315 
Solid  reamers,  144 
Spacing  gauge,  307,  308 
Spanners,  172,  173 
Speeds  control  tool  angles,  15 

—  of  emery  wheels,  194 

—  of  drills,  in7,  138,  139 

—  of  grindstones,  192 

—  of  saws,  82 
Spiral  punch,  160 
Spirit  levels,  243-246 
Spring  of  tools,  59,  61 
Square-centre,  238 

—  combination,  238 

—  combined  with  rule,  225 
Squares,  234-239 

—  correction  of,  235 

—  fitting  blade  to  stock,  235-237 

—  testing  of,  234 

Staggered  toothed  mills,  73,  117 
Staggering  of  teeth,  73 
Standard  bars,  220,  221 

—  bars,  flexure  of,  221 

—  bars,  transference  of  dimensions 

from,  223 

—  bronze  bars,  220 

—  lengths,  tests  of,  223 

—  rules  and  rods,  229 
Standards  of  measurement,  218-224 
Straight-edges,  50,  230,  231,  232,  233, 

234 

—  how  used,  233,  234 

—  origination  of,  230,  231,  232 
Stropping  edge  fools,  201 
Support  afforded  to  tools,  15,  16 
Surface  gauges,  247-261 

—  plates,  231,  232 
Swages,  169 


Taper  drill  shanks,  142 
—  of  punch,  161 
Tapers,  gauges  for,  322 
Tapes,  228 

Tapping  holes,  gauges  for,  320,  321 
Taps  and  dies,  1 51- 159 
—  and  dies,  action  of,  151,  152,  153 
—  backing  off  of,  154 
—  relief  of,  154 
—  set  of,  153 
Tap  wrenches,  174 
Teeth  of  saws,  79,  80,  8 1 
Temperature,  217,  221,  222,  296 
Temper,  drawing  of,  185 


Tempering  tools,  182,  183,  184,  185 
Templeting,  330,  331 
Templets  and  jigs,  331,  332 
Testing  gauges,  316 

—  squares,  234 

Tests  for  standard  lengths,  223 
Threading  tools,  61 
Tolerance,  limits  of,  310,  313 
Tongs,  175 

Tool  angles,  6,  8,  10,  ii,  12,  58,  210 

—  angles,  a  problem  complicated  by 

many  conditions,  19 
— ■  definition  of  the  term,  I,  2 

—  grinders,  water  trough,  195-209 

—  grinding,  187,  188,  189 

—  grinding,  precision,  202,  203 

—  grooves,  64 

—  handles,  177-181 

—  sharpening,  200,  201,  202 
Tools,  broad  finishing,  59,  64 

—  cranking  of,  58,  59,  60 

—  for  arboring,  77 

—  for  brass,  60,  62 

—  for  boring  wood,  120-126 
— -  for  finishing,  59,  64 

—  for  measurement  and  test,  215-333 

—  for  moulding,  168-171 

—  for  planer  and  shaper,  59,  60,  61-64 

—  for  planer  and  shaper,  speeds  of, 

65 

—  for  parting  off,  59,  60 

—  for  shearing,  69-74 

—  slotting  machine,  60-68 

—  threading,  61 

—  general  remarks  on,  1-5 

—  hardening  of,  182,  183,  184 

—  inside,  60 

—  right  and  left  hand,  59 

—  roughing  for  metal,  58,  59,  6 1 

—  science  of,  13,  14 

—  spring  of,  59,  61 

—  tempering  of,  182,  183,  184,  185 
— -  used  by  moulders,  170,  171 
Top  side  rake,  59 

Topping  saws,  87 
Trammels,  267-270 
Trimmer,  70 

Truing  emery  wheels,  195 

—  grindstones,  191 
Turners’  scraping  tools,  76 
Turning  chisel  for  wood,  33,  34 

—  gouges,  36,  37 

—  tools,  handles  of,  179 
Twist  drills,  131 

—  increasing,  132 
Twisted  bits,  123,  124 
Types  of  saws,  81 


340 


INDEX. 


VERNIER,  279,  280 

—  applied  to  scribing  block,  303, 

304 

—  calipers,  281-286,  291 
—  depth  gauges,  303-305 
—  height  gauge,  303,  304 


WATER  on  grindstone,  193' 

—  trough  tool  grinders,  195- 
209 


Wear  of  calipers,  290,  291-293 

—  of  gauges,  31 1,  315,  316 
Wedge  gauges,  322 

—  like  action  of  chisel,  23 
Wet  grinding,  195 
Winding  strips,  50,  234 
Wire  edge,  201 

—  gauge  and  caliper,  324 

—  gauges,  323-326  _ 

Wood,  tools  for  boring,  120-126 
Woodworkers’  gauges,  307 
Wrenches,  172,  173,  174 


Printed  at  The  Darien  Press,  Edinburgh, 


4  ‘  / 


